Best wishes and prayers to you. Very few things in life worse than being underemployed, underpaid and underappreciated all at the same time.

Once quit my job due to integrity issue (my boss had none, I had enough to realize what was being done may have been legal but unethical) and left a $60,000 a year job with lots of benefits for a $28,000 with medical benefits, vacation and little else. At the time it hurt like hell, my wife and I had to scrape for every single cent (and I was starting grad school) but each day it got better everytime I looked in the mirror and realized that money is just a tool, albeit a necessary one. Knowing that my honesty and character are still intact is worth more than any money right now.

Hang in there.