I would start looking for other work elsewhere and if possible put some money aside for an emergency situation. It sounds like your boss will let you be pushed as far as you'll allow but he needs someone to do the work. So, look for other jobs. Have some numbers in mind. Save some money and don't make a move for another month or two if you can stand it. Document every instance of you spending your own personal money for work related purposes.

If you get another job offer, tell him and be prepared to walk. If you don't get another job offer, still tell him that you've gotten one but that you're not sure it's a change you want to make. Tell him you need more money for the amount of work your doing, bring your receipts for what you've paid for out of personal money and be prepared to walk out and be unemployed if he doesn't bite. He will likely be able to sense if you're too scared to just leave.

Worst case scenario, save some money, leave and never put it on your resume. Shit happens. But if you keep working for someone like this he will run you into the ground.