desperately, really interesting to have your backstory.
When I met DH I was so completely convinced that the relationship with his ex would be resolved. He left after she had multiple affairs, I wasn't involved. My approach was that we would always do the right thing for his child and we would always be patient and understanding. My relationship with my ex had been positive so I knew it was possible.
However after many, many years (during which his ex married and divorced again) I've had to accept that no amount of goodwill from us would make his ex reasonable. Sadly we have had to go to court to get a contact order as she refused mediation or any reasonable attempts of conversation. She has treated her latest husband appalling and she has moved onto another partner. I had hoped that would have an positive impact but it doesn't feel as if we have turned a corner yet.
What you highlight is that you made the personal decision to be reasonable, after your Dh had asked you to and you are fortunate that your ex responded in kind. However what most of us are dealing with is an ex who refuses to respond positively - no matter how reasonable.
If we all had reasonable ex's who did co-parent then we this forum would be empty.
Just to clarify - I do not spend 15% of my income plus CB on my child..no way, if that was the formulae then no family could have 4 children as that would equate to 60% of income to support a child PLUS housing and car costs, bills etc. Interestingly, banks have an assessment of what it costs to be a family when assessing mortgage affordability and they do not use anywhere near 15% of income for each child.
My DH contributes 15% to his ex, plus we have housing costs for him, we have similar sized car (since he needs a seat when he's with us), he has clothes, bedclothes, food, haircuts, holidays etc.