My friend isn't on-line tonight, apparently, so I don't think I'll get a response from him before tomorrow at the earliest.
I can answer your first question, somewhat. My friend dropped out of college after his first year and joined up. He was regular army for a couple of years, and served a tour in Germany. He then joined the 82nd Airborne so he could come home (he's a North Carolina native.) He was Airborne for a year or two, then tried out for Delta. He failed the first time because of a severely sprained ankle (didn't pass the physical endurance tests.) He tried again the next time he could, and got in. Getting into Delta requires a LOT of determination.
I'm certain that he's had a helluva lot of specific schooling, but to my knowledge he never went back to college and got a degree. He retired as a Sergeant, I'm not sure at what level though. Sounds like you want to go officer.
I asked him one time what, exactly, he did. He said "I get up and go to the base, do P.T. (physical training) for half the day, shoot for the other half, and go home. And they PAY ME!"
I know he's been all over the world, and he's done some hairy sh!t he won't talk about, but mostly they train. A lot. They travelled out to Tucson for jump training (and, I think, ground assault practice on parked airliners at a nearby air park.) I've seen his team practice at an indoor range with their .45's. I wish I could shoot half as well.