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?
1. Yes. I said that I have nothing to do there, I don't see the point of coming just to hangout. The reply was that they'll find something for me to do. The manager took it as their fault, as if if they're unable to find work for everyone until they collapse on the couch they're not doing their job.
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.
You should quit immediately. Also, please see cperciva's comment above.
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.
* You don't owe them anything * They, as a company and individuals, do not love you * This isn't what you're passionate about
If you have the finances to survive for 4-6 months and no (or manageable) debt, I say quit.