Cut back and smell the roses. Life is a marathon and not a sprint. Reduce hours to the better job and possibly school hours so you will do better at both.

16 credit hours and 75 hours working would be too much. very unlikely you'd get over 40 hours at one job - fast food rarely goes into OT pay hours, no way it'll be 50 regularly, probably not at all.

There is nothing wrong with working that many hours as long as you have your priorities straight. Which means getting enough rest and keeping up with your schoolwork. I would cut back when I went back to school, if you can financially afford to and/or if you have a lot of social activities.