1) Not all totems are created equal, and they don't spin unless they were physically designed to do so. Like Cobb/Mal's top. The mass/weight/design of the top is the importantelement here. It's the fact that in a dream, the dreamer can will his top to continue spinning. If it doesn't continue spinning and drops eventually, then he is reassured that you are not in dreamscape.

ie. Arthur's totem is a loaded, six-sided red die. In reality, it should keep landing on the side where all the weight is distributed. However, if it keeps rolling random numbers, he is still dreaming.

2) A "kick" is not just about the SENSATION of falling. It can also be drowning (like when Arthur pushed Cobb into a bathtub filled with water) or other events/actions that is programmed to wake you up. When they went in Fischer's dream, all the kicks were programmed to coincide with the Edith Piaf song “Non, Je Ne Regrette Rien”. Then the dreamers would choose whether to go along with the kick or stay. Think of the kick as your only chance to get out of a locked room with no entrance/exits.

And dropping off the ledge was not the kick. It was the blast that was going through Fischer's subconscious that was the kick (heart defribillator->hotel elevator explosion->van crashing into water). Ariadne rode the "kick" wave back to reality.

3) How do you know if they didn't spend months/years in the 2nd and 3rd levels of the dream? Maybe the movie showed us the final events (action scenes) instead of everything that led up to them because it didn't really serve a purpose. HOWEVER, the time differential -slash- "screw-up" was explained in the movie. In the 2nd level of the dream (hotel), Cobb and his team revealed to Fischer that he was dreaming and tricked him into thinking his subconscious defenses were the extractors and the true extractors were his protectors. They tricked him into helping them which sped everything up. They did not have to spend so much time building a relationship with Fischer.

Saito was stuck in Limbo, and as it was seen with the Cobb/Mal flashback, time moves faster. That's the key here. It's not time that's moving slower IN the dreamworld but faster compared to the waking world. That's why Saito, Cobb, and Mal had time to grow old and such in their fabricated world. That's why Cobb says he was "an old man, filled with regrets".

Cobb was searching for Saito for 20 years (I think) in the dream world, and finally washed up ashore to Saito's subconscious core. But, Cobb knew himself to be a dream construct, so he maintained his young appearance.

I hope that helped.