You neatly compiled the options and ideas here. Nice work.

I'm almost at the point where I don't wanna guess about much of anything anymore. Too much has been left in the air - so late in the series! - for me to feel like there's a whole lot of "terra firma" upon which to stand.

I would like to point out, though, that you're patently wrong about Rand+Moridin= 2 become one. Ever since the Rand/Sammy SG battle, LTT has been referring to "that other guy." We know that person is Moridin. LTT and Rand have always viewed themselves as separate individuals (until end of TGS counts as "always". Thus, LTT and Rand and Moridin are all in Rand's head, and thus are three that "can" become "one."

Lots of people have run with this theory. Lots have connected it to the dreams/prophecies about Rand removing masks from his face and one of them becoming real. I don't know that these two separate prophecies "must" be connected, but it always sounded quite right to me...