Regarding Tony's motivations in IM2, a key piece is the whole idea that the movie set up of Iron Man being an important strategic asset. I think the angle was overplayed (IM isn't on Doc Manhattan's scale; and what's with "stabilizing East/West relations" in 2010?), but that's where the filmmakers were coming from. Tony had a responsibility to be Iron Man, not a reclusive playboy plugged into a car battery...a responsibility that Rhodey taking the spare armor must have relieved somewhat, when all was said and done. That was also what Vanko's plan was about...he wasn't threatening Tony himself, he was threatening Iron Man's image. It was about the genie that Stark had let out of the bottle, the beginnings of a new arms race, and Tony trying to stay in control of the situation.
Plus there's the alcoholism to factor in...the guy is prone to self-destructive behavior. What to choose...playing it safe plugged into a car battery, or being one of the most powerful figures on the planet...?