WTBH, with all due respect, it seems to me your gut is saying something different, because everything above is your head talking. And as a long-time single parent, I understand your financial concerns. I have lived this life for over a decade now, including unreliable child support.
However, I refuse to have a job I don't like. Lexie is right - it is a huge amount of time and emotional investment. I am actually looking at a similar situation here right now, only its choosing between a job I love that doesn't pay well for a job I might love that pays fantastic! And I am grateful I can choose! Haven't decided yet...
Take your ex out of this decision. Being angry with him is complicating it. Play the tape forward - what if you scrimped and saved and clipped coupons for a year to take this job and see how it goes? By now, you have some special ed experience under your belt, right? You could go back to that if this isn't quite up to par, right?
Picture what it would be like to go home every day happy and content. Will you get that where you currently are? If not, take the new position. Believe me, it will all work itself out. I never ceased to be amazed at how much I worry and fret over that never actually happens!
I'd be teaching what I LOVE most (social studies to middle school kids vs special ed which I fell into a few years ago and have found it hard to get out of and back into social studies in the traditional public school setting).
I used to teach middle school Social Studies and LOVED it
To me, this is your gut talking. Notice how much of an emphasis you put on "love".