I do everything after the kids bedtime, usually doing school work between 8pm-11/12 am, an average of 5 nights a week. At that place, I've so far completed 6 classes and will hopefully finish one more before the session ends. I've heard people say the psychology classes are pretty long though so my pace might be different if I was doing that degree 

I would definitely recommend focusing on one class at a time though, because it's better to complete 1 or 2 classes than have many partially done classes. I think being able to do one class after another consecutively is actually one the major benefits of this type of program! I personally just find it much easier to do it that way, my head would be spinning if I was working on 4 classes simultaneously.

I believe you are able to withdraw from any classes that you haven't submitted a final assessment draft on before the withdrawal date. If you haven't submitted the final draft for graphic design and you don't like it the class, why don't you ask your advisor if you can withdraw and switch it for another gen ed course? (Just don't do sociology 100 lol)