No debt, lease expires soon, savings for ~3 months.
Is the company DNA so focused on 60-70hrs/wk that there is no middle ground?
* Can you negotiate a raise?
You say that you're earning the least per-hour you have for 3 careers. Can you negotiate up? Sure, you hate it now, but if you were earning another 10-20k/year, would you still hate it as much?
* Can you get fired?
If you just work 40hrs/wk, will you get fired? Would you mind that?
* Can you stay on and build a network?
Can you keep drawing a paycheck, working 40-50/wk, and build a network to find another job or entrance to an art program?
2. No. I hate it.
3. I don't mind being fired. If I work 40hrs/wk I'll keep getting terrorized with voicemails and text messages in the evening and on weekend. It sucks.
4. I signed up for a bunch of art classes at colleges in the evening, but quitting will allow me to expand that into day as well.
Take a complete break for one full week, before making the next move. That will help you take a better decision on what to do the next. Go and meet deep personal friends, you'll need them while you decompress your mind.
After that, start networking like a maniac, showcase your skills in communicating with {people,computers}. While you're searching for the next job, it is a great help to be a part-time faculty at a computer institute.
Good luck.