Please note that anything I say here is out of sheer empathy and me feeling very much how you have at one point.
I am still trying to wrap my head around why you are refusing any sort of financial support for your kids. While your ex was very disrespectful in the way he said it, he has a point. he admitted that he couldn't do this financially if roles were reversed. That him having you on his insurance, or easing the financial load for you where he can, is beneficial to your kids. You should be proud of the job you love, absolutely. he was a real dick for saying otherwise.
My ex left me with a baby and I was the main bread winner. So, I got the joy of paying for majority of her very expensive childcare. And just a bit in child support. And majority of the custody. To this day (9 years later) he pays what he should and not a penny more. Literally, not a penny more. Heck, if he wanted to throw me extra, I would grab it in a hearbeat!
I was where you were, all "he left US" I don't need this, I don't want that, you ditched your family, we don't need you..."
Reality is, my daughter needs her father. Else we would be so far away right now. Some parents take care of their kids in different ways. If he wants to financially support the kids, don't be a martyr because you are hurt by him leaving. let him do this. Not to absolve him of leaving. Not absolve him parental negligence. But it only hurts the kids and you to not take it, or to argue it, or to give him the same speech. (I gave my ex the speech all the time "I was a good wife, I loved you, you left our family, you cheated, blah blah blah", he learned to blank it out).
You are the mother of these children and you are doing an excellent job. But being the martyr is exhausting. Take the money for the younger kids, let the older kids handle the money situation with their dad, and you decide what is best for you financially. Stop worrying about what he thinks when he gives you the money. he only has as much power as you give him over your life.
