Dulcinea,
This sounds like a very frustrating situation to be in.
I agree with others that you are being grossly underpaid.
It seems that one of the main challenges is that you are located in an area that has abyssmally low wages for your skillset, but that you find it difficult to leave. (And, as you say, you tried that and it didn't work... and it seems you aren't excited about trying it again.)
The logical thing, as some have mentioned, is to move somewhere that your skillset will be more highly valued. In my area, a nanny watching two kids (often from separate families, in a nanny share) makes $40,000/year or more, and in many cases has paid sick leave and 2-3 weeks' paid vacation.
There are some skills and mindsets that can ease the transition away from your family and hometown. I would recommend you explore learning them. Do you have friends or acquaintances who have moved away who you could contact? Would it be helpful to not go _too_ far away... perhaps St. Louis, Dallas/Ft. Worth, etc.? I bet there are message boards/internet communities dealing with this.
And, if you like, you might elaborate right here on what is preventing you from moving, and what caused you to return in the past (ran out of money?).
I know one barrier to moving is not having much/any cash on hand, but this is surmountable, in particular if you can get a job offer before moving, although that's not required.
Logistically, I know what plenty have done is crash with a friend/acquaintance for a week or month while they find work.
Ok -- I've been avoiding your actual question of whether to go back to school. It's completely reasonable... but I think you're more likely to be successful and happy with it if you first find a way to sustain yourself, and approach it from a position of strength. Right now, in your current terrible situation, it is possible that ANYTHING that looks like an escape hatch will appear extra enticing. But you have lots and lots of options in reality, and some of them don't have additional major debt attached to them. I think your time and energy will be best spent trying to significantly increase your income and stop being taken advantage of. If you can do that in your current location, great, but if not, I think you should focus on how financially and psychologically prepare to relocate ASAP.