I'm a full-time grad student in a combined dietetic internship program with a graduate assistantship and a part-time job. Essentially I work 60 hours/wk minimum with 40 non-paid, but I enjoy that portion of it. My graduate assistantship is working in an animal research lab and publishing some of the data, which I also really enjoy. Overall, it's pretty hectic but manageable as long as I stay organized and don't take on too much extra on any given week. Keep in mind, I graduate in December so some of this will curb before I really hit the books hard for the MCAT. Then again, I will ideally be working full-time as a dietitian at that time.
It sounds like you need to put in a lot of your time during the weekends. Previously I would wake up by 4 or 5 in the morning to study for ~2 hours each day. I still get up most days at that time, but I don't think it's sustainable if you do that and stay up late. I always found if I stayed up too late I would finish reading something and have no idea what I just read, much like trying to read a book to fall asleep. I always try and handwrite notes even if it's something simple because I seem to retain it better and can always look back to see what concepts I just read.
Hope some of that helps.
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