Hello AV ...
I'm probably the only man responding to this, but it may be, at least, from a slightly different viewpoint than your other replies. I'm sure you are aware of this but .... whatever you do, don't do it at the expense of the children.
If your children really like or love their Dad (first marriage), don't use them as any kind of bait for child support. The child support should always have been there ... even if it was only a percentage of unemployment for the period of his unemployment. Do whatever else it takes to collect that child support - and back child support, if it's due!
I, personally, am the result of a divorce (when I was a year old) and my Mothers re-marriage (when I was 5-years old) ... and ... I loved both my Dad and my Step-father.
My own divorce of over 20-years ago might be an example of how it can affect children when pressure is put on them. My child support record was 100% clean (never missed or shorted) ... and I saw them every other week-end and for two weeks in the Summer and some of the holidays. As I later found, my Ex was making nasty comments about me during some of those years ... and she did hold the kids away from me on our first holiday after the divorce - so I could not see them.
The results, 20-years later ... I see my oldest daughter now taking advantage of her mother financially ... and my youngest daughter has not seen her mother for a couple of years - and we all live within 40-miles of each other. To me ... it is sad! I don't want to see my Ex treated that way, but it really isn't any of my business anymore. One daughter is 37 and the other one is 28.
If a marriage counselor to save the marriage is not realistic or even possible, you should be able to get 50% of whatever the balance is of the total net worth ... or the assets minus the debt! And that would be just the beginning - before child support (if due) and alimony (if applicable). Any decent attorney would know far more than I about those things.
And it does sound as though "taking care of yourelf" is something not to dismiss ... and I'm talking about your emotions!!! Don't ever feel you are the cause ... get counseling help. I have had experience with that myself long ago when I sought a counselor ... and I found a good one - and with an agency that worked on a sliding scale for cost (thru the county). As I recall, it cost me $24. per private session ... and it was the best money I have ever spent.
I know ... this was long ... but it was from a man who is no longer bitter about his ex-wife. Think about that!!!
Good luck to you.