I understand your concern and the suggestions here are great, but Jen, one thing I want to add is please try not to add to your stress by projecting that he is going to become his dad. It won't help you with your worry and he may sense that too.
Great ideas above and I do agree with Helpus that kids are used to those hours while in college...kinda like being babies again; they get their days and nights mixed up, lol. Since you feel new to this boundary game, what of all the suggestions given, can you do and stick to? Perhaps start there. When my daughter was staying with us, I told her the curfew boundary was for me, not her. I needed to know she was home and safe or I could not sleep. She respected it more once she understood that it was not an attempt to control her. She was 19...my curfew was midnight during the work week and 1 on weekends. I told her that her friends were welcome to come home with her to stay over or to quietly talk.
The part about not continuously waking him up is hard, I know...but I think that is a consequence he has to face. If he knows he can count on only one call or just his alarm; he'll get there...He has to at college, right? I suspect your other son will support you in that boundary.
As to chores...well, I realized that my version of clean was far different from my kids, so I had to be specific in my requests for assistance. If I was and I provided a reasonable time frame to get something done, i usually got positive results. Not necessarily done to "my standards" but as long as I had no expectation that it would be "my" way, no sweat
Good luck Jen...I know it is hard when this is new, but if your motivation is to relieve your own stress and have a more relaxed home life rather than to control your son, I think he'll understand and respect boundaries a bit more. Hugs and prayers.