See, I basically put that down to a cynical propaganda maneuver. Ordaining NKVD agents as priests to use the church as another agency of subversion doesn't sound like the actions of a superstitious man afraid to cross whatever God might be letting him get away with his shit. And it could be that he was willing to let a complacent and subordinate church carry on as an organ of state control. In any event, his continued "tolerance" of the church, or even the potempkin village of a church he allowed to exist, is a strong argument AGAINST his ideological purity. A true believer might reluctantly accept its existence as long as it was useful or necessary, but not a moment longer.
Never said he was dumb. IMO, he was a lot more sophisticated than the ideologues. If the Party was giving out grades before the Revolution, he might have got straight 5s in socialism or Marxism or Leninism, too. Plainly, as his religious grades indicate, there is not necessarily a correlation between school marks and lifetime performance. American history has more than a few successful generals whose academic performance at West Point was substantially inferior to Stalin's seminary grades. Also, given his approach to the photographic record, can we be sure that no one paid a visit to the Seminary to alter his transcript?
Again, not relevant to his style and motivation of leadership. Assuming he really wrote it.
I interpreted that it was about control. He was paranoid (those feasts to which you allude had a kind of compulsory attendance, with people forced to indulge lest Stalin see their restraint as an insult, or interpret them as trying to stay sober to gain a tactical advantage), and throughout his administration (or more accurrately, reign), systematicaly eliminated one potential power bloc or rival after another. The collectivization and so on was a way to eliminate what passed for a middle class in the agricultural sector.
Seeking to acquire force at arms is exactly what a paranoid thug would do. By contrast, weren't socialist ideologues of his generation anti-military?

Exactly my point. An ideologue would have had at least an abstract concern for the people's welfare (hence Lenin's NEP). Military hardware benefits the government, especially in a highly centralized state. It should be noted that Stalin was fairly inept at every aspect of military leadership, aside from maybe the propaganda parts, and keeping himself in control. His involvment with the military tended toward things like replacing competent (for Soviet values of the term) generals with cronies, shooting anyone who came to him with news he didn't want to hear, like the head of the Air Force, for bringing up quality control issues that were causing plane crashes, and even at one point, meddling with artillery production, getting a late start on production of the superb 76.2mm anti-tank gun in favor of old fashioned howitzers, because he was familiar with the latter from the days of the Revolution and Civil War. That former gun was so effective the Germans repurposed the significant portion of their armor pool & tank industry which was obsolete and undersized to carry captured Soviet guns, which is where the original Marder series of armored fighting vehiles came from.

That actually speaks more to the shortcomings of the Nazi military than anything else, as their production was dilatory and more focussed on being able to say they had a certain number of tanks, rather than producing effective weapons. Production of the Marks I & II continued in parallel with the IIIs & IVs that were supposed to replace them, with a reliance on captured enemy equipment that is pretty astounding given the general historic reputation of Germans for industry, innovation and technological superiority. The Soviet machines were intended for the use of unsophisticated peasants, so it was relatively simple for the Germans to adapt them to fill gaps in their own TO&E. On the other hand, a great many of those tanks could barely operate, the Soviets had a severe shortage of spare parts, their supply system had trouble keeping them running or fueled, and their operational life in many cases was barely sufficient to train the crew. There was nothing superior about their construction, although their design was very good in several respects (not least that 76.2mm gun), largely due to foreign contributions, such as Walter Christie's suspension, or the Vickers tanks that were the basis of the T-26.

Furthermore, most of that army's commanders were in over their heads, having been promoted way above their capabilities, due to the gaps in the chain of command left by Stalin's purges.

Whose chief had been executed, as mentioned above, and which still needed planes donated by the Western Allies, until their own efforts whittled down the Luftwaffe, in addition to sufficient time having passed for the late Wever's vital contributions to have faded and it was entirely the work of Goring, Milch and co. Under Stalin, the Soviets were not exactly facing the peak of German military prowess (however more impressive the swath of territory to fall under Nazi control is than Imperial Germany achieved), but were being slaughtered in vast numbers. He could make speeches about his inexhaustible manpower, but the USSR's population was roughly twice that of Germany & Austria (as best we can tell, given that Stalin shot the takers of the last census during his rule for producing results that fell short of his predictions), but the Germans were killing Soviet troops at rates of 3:1 or worse. The Soviets had a significant armory but that bears as much relationship to a functional military force as a ream of paper bears to a novel. And this was largely the result of Stalin's management.

I just don't see how enumeration of Soviet hardware demonstrates Stalin's ideological credentials. It's like saying that having a gun collection makes you a sincere follower of Buddha. It doesn't even make you a credible soldier. Thugs want muscle, because that's what they understand. Yes, Stalin was an intelligent and sophisticated gangster who grasped better than even many PR professionals the psychological aspects to power, but in operation, he was still the head of a thuggish government, built largely in his image by his sycophants.

Or was using them as an excuse to expand his power and eliminate any possible threat to his regime, even ones that existed only his imagination. He lasted as long as he did and rose high among the revolutionaries, because he knew how to talk the talk. He also knew enough to dial it back and assuage foreign leaders, given how completely he pulled the wool over the eyes of Roosevelt and Truman. IDK whether Churchill was taken in by Stalin, blinded by decades of anti-German politics, or cynically trying to play off the USSR & USA to maintain his own (and country's) prestige as the very junior partner of the alliance, given that everything else in his career outside of his dealings with Stalin suggests he should have known better than to let Stalin get the better of him as he did.
Or he was playing hard to get, establishing a high initial negotiating position so that he could "settle" for more than he might otherwise get. It could also be that he was setting up Zhukov to take the blame in case everything turned out badly. He could have been playing humble for his image. Or he could have been sincerely disgruntled over the thwarting of his ambitions, and hoped to push his empire farther west.
But a revolution that answered to him. I don't see much to indicate he gave a shit if it happened without him, beyond possible self-serving declarations of humility.
That proves ambition, not sincerity
Another interpretation is that all he had were reports, not proof of intentions. IIRC Hitler ordered the attack on France nearly a dozen times between the fall of Poland, and the actual attack on France, and that attack was also delayed by the Scandinavian operations. Knowing that Germany was preparing to attack the USSR wasn't the same thing as believing an operation was about to kick off. He probably expected the campaign to actually start at the beginning of normal campaigning season, as you say, in 1942. Aside from the units being so far forward, there was also the transportation infrastructure, which was mostly built on an East-West axis. Defensive preparations would have been built parallel to the frontier, so as to facilitate moving troops from one part of the front to another in response to enemy attacks. The Soviet military preparations near the German border indicate a concern with keeping men and supplies moving forward.

But as I said, these are equally believable as the actions of any conqueror or tyrant. Communism simply provided the labels which Stalin used to create a facade of respectability for his actions in support of his personal power. Lots of rotten people gamble their lives and futures for greater gain, even when they already have what seems like it should be plenty. Ruling a greater land area than any other man alive might seem like enough for most people to relax and coast along in a presidential palace, garnering praise by tossing crumbs to the peasants and posturing for foreign journalists, like a commonplace dictator, but Stalin was one of those people who wanted more power, and so he took risks to get it. Boldness is not, and never has been, a characteristic entirely reserved for believers. As with Hitler, it might too have been that some of his risks were less than it seems, because he had a better assessment of the opposition than many others did. Since his risks largely paid off with success and power for himself, you can't say for sure that he was nobly betting his own interests to advance the cause. Maybe he had the deck stacked, or knew that his chances of success were better than conventional wisdom assumed. Maybe he didn't care to survive in a world where he was forever locked out of the highest circles.
Maybe because he perceived Stalin had none, or that such an accusation would not sting Stalin the way it would the others, who seem to have sincerely believed, and acquiesced to their own downfalls in keeping with their assertions of the primacy of the Party.