feel for you man, reluctant to give any advice as it may be wrong.
in a similar situation as you 10 years ago.
our split was forced on us but it was probably the best thing that happened to both of us, at that time!!
i met and am in a a relationship with a wonderful girl, but my ex poisoned the kids view on me. My step daughter hasnt really talked to me since i left, and my son cant be bothered and doesnt get in touch anymore.
so for me, the cost of freedom and a new relationship with a new partner was not seeing the kids, tough choice.
if i had known what i know now before the break up, i would have done exactly the same, but found a different way to perpetuate the relationship with the children, not sure what though?
oh and it wasnt exactly financially beneficial for me :-(
good luck, maybe put it to one side, enjoy the kids and spooning with the missus until after xmas at least