Justin, I'm a second year student and a ROTP applicant but I'm not sure if I want to still stay in school, and may just go Reg Force anyway.
1(2). My cousin was a big hockey player. He did one year in the NCAA before playing in the AHL, German Elite League, NHL and finally ECHL. He went back to university at 26 years. He had his one year of school when he was young then chased down his dreams. He told me that he was happy he waited, he was older more matured and was able to pay for his own schooling using all the money he earned playing hockey. He didn't have to take a loan or ask his parents for money. 3-5 years when your 21 isn't long, you still have a lot of time to finish your schooling if you do one contract and leave. You'll leave with money saved and a different outlook on life.
2.5 Being in university for two years I can tell you that its a bit of a mix. My first year I did at Queens and for me that was what I thought university life was, partying all weekend long with pretty girls and my football friends. School was "optional," and I was writing 3 papers per term for my classes. I had an insane amount of free time and could do whatever I wanted and was surrounded by my best friends from highschool. I did okay, I finished out with a B-/B+. This year I'm at Carleton and I'm writing 7-8 papers per term, my classes aren't so optional because of my program, I blew out my shoulder last year playing football so that's done. So yes, missing out some university sucks, but its mostly first year that's a big party and thats only for a few months and then it dies down. So I mean you wouldn't be missing much, nothing you won't do on weekends with you course or platoon mates.
Hope that helps from a civi perspective.