Definitely complete IOE and spend at least a little time online. If you think you might want to come back and fly for an airline someday, do not quit during training, even if they try to intimidate you into thinking that you might get canned. Even if that's the case, get as much out of the experience, personally, as you can and let THEM tell YOU if you aren't going to make it. That's better for you, even though it's tough, and it's far more respectable than quitting because there was an arse hole instructor. There are some of those everywhere. It sounds like you got through the worst of it, so stick it out a few more weeks.
After you do that, definitely go back to school and finish your degree however you want to do it (I would say that finishing up part-time while flying would be best, if that's an option and you want to stay in the industry). Don't listen to anyone who says you don't need a degree to be a pilot. Even though there are plenty of pilots without degrees, my arguments are these:
A. It sure doesn't hurt you or make you less competitive.
B. If for ANY reason you lose or leave your pilot position, say when you're 40 (medical, company bankruptcy, whatever) finishing that degree at that point may be a lot harder than it is now, but having it will make you far more employable in higher salary ranges.
C. Finishing the degree is a challenge to many people, financially and otherwise. Completing it shows that you persevered.
D. Aside from the workplace, education, in and of itself, is a good thing.
By the way, you're not alone. Many of us have had a sh1tty airline training experience or two that really knocks the wind out of you. A little time and experience will give you a much better perspective on that (i.e., you won't give a crap a year or two from now).
Take care.
Lebowski