Keep up the good spirits! I know it's hard sometimes, but you have such a drive that I'm sure there can be no stopping you.
I can relate quite a bit. Although I do have a husband who is very supportive of me, he makes little more than minimum wage. He's in college right now and his current job allows him a lot of time to read. It's one of the sacrafices that we make right now for our goals.
When I decided to 'come home,' I sold my car to get rid of the expense of it and started doing some home sales parties as a way to help with the transition. I've since been able to make income from some of my creative skills, doing graphics and making web pages, and although this can hardly be considered an income it does help here and there. Also, I flipped through some books on living cheaply... the book "Miserly Moms" comes to mind. Not only do these books show you ways to save money, but also point out the expense of working itself.
I also only paint in the evening. Although I'm home during the day, I homeschool my son and I do not have a seperate room or area for a studio that I can escape to here and there during the day. So, when he goes to bed at 7:30 or 8 is when I start, and I usually go until about 11 or 12. I just try to keep reminding myself that it is do-able. I am getting work done, and although it is not at lightning speed I am continually moving forward. Try to think of it that way for yourself... you are moving forward and your work is great!
Resentment... no advice there! I do catch myself thinking "What?!? You don't want to do math? I could be painting!!" but at these times I just try to let my mind go completely blank. I don't want to have a panic attack! If worst comes to worse, I try to think of the numbers 1-4, very slowly, over and over again.
Have you thought about working part time instead of full time? I don't know what kind of job you have, but if it is a low paying job maybe you could look for a different kind of job that lets you be more creative. I know I always see jobs for ad layout at the local newspaper. Also, you can always see about making money teaching art. I know that you mentioned trying classes at your home, but there are also opportunities at the art stores and at local art centers. Maybe if you have to work but the job relates more to your passion, you will feel better at the end of the day.
Good luck and I hope that some solutions find you! I am one who thinks it's OK to sacrafice for art, hey there are always soup kitchens if you need them, LOL! Just keep yourself healthy.