hi Miia,
Sending you hugs! Being a friend/caretaker of someone struggling with mental illness is a lot of work, and as you support him, you should not forget to take care of yourself. I suggest journaling, keeping up with your regular hobbies, etc. Also, your university might have a counseling center, if you need some extra help to handle the stress. And expressing your frustration on the forum is okay
Some thoughts:
-why is he reducing his medication? This seems like a strange decision to me...if he didn't sleep for eight days and tried to kill himself, his psychiatrist(s) and/or social workers absolutely must know for his safety. To me, that means his medications aren't working.
-he absolutely needs to see a therapist. You can support him, but he needs professional help.
-I like the idea of exercise and cleaning routines. Some mood therapy workbooks (e.g. Mind over Mood) suggest rating activities based on pleasure (1-10 how much did you enjoy) or mastery (1-10 how well did you complete the task). Few people actually enjoy house chores, but we do need to master them to take care of ourselves.
-maybe you should make to-do lists together? You can still "schedule" time for him to sit and watch movies - in fact, a more gradual transition will probably more effective - but also schedule exercise, grocery shopping, etc.
-If his house is really so messy, I would suggest scheduling 15 minutes at a time. I think it's much easier to start on a big task if you can say, "well, if this is really stressful, I can stop after fifteen minutes" or "I can't clean the whole house today - how overwhelming - but I can at least do fifteen minutes of cleaning."
Also, when I was in a mood therapy program, we were often asked to rate our moods and anxiety levels before and after activities - we did this in order to notice the effects on our health. Almost universally, moods were higher and anxiety was lower after playing games, doing exercise, etc.
I hope some of my comments are helpful!