Excellent advice a few posts up from Nicenewdusters.
Like loads of posters on here, I admire your integrity, your strength and the way you're handling this.
You must though stop reacting to him. It's his choice to rush along with his new rental. He will have to fund that and it has no bearing at all on your situation. He will stay on your mortgage until the time it is transferred to you. He will be liable for his share because if you can't pay it, the lender will go to him. Regardless of his rental, he's duty bound to pay the mortgage. So please stop worrying about this.
The kids situation, I nodded and sighed when I read about the inevitable crash. It brought tears to my eyes actually because I remembered dealing with the same reactions. Different kids, same reactions. My DD desperately wanted a dog, for years and years. I was neutral, but ex adamant that we would never get one. He sets up home with OW, he gets OW a lab puppy. DD in tears, because in her mind dad loves OW enough, but he didn't love her enough. As a 15 yr old she couldn't see that practically OW had the time, because she mainly works from home, to look after it, she saw rejection. Anyway we had tears, then we had rage, then withdrawal. And naturally I had to deal with it. Like you, it's really hard, when you're emotionally on your knees, to have one more thing to deal with.
I coped, you will cope. I stayed consistent, listened, supported her. That's all you can do. The 'puppy' incident raised its head in different guises for all three over the next few years. All I could do was rage inwardly at the selfish, thoughtless behaviour of their father whilst plastering on a smile and being there with cuddles and support.
It's hard, it's unfair, but it's the way for countless mums in our position.
And it doesn't last forever. Remember this. Mine are all young adults, they totally have the measure of their father, and he's paying the price. A litter of puppies wouldn't make his DD closer to him. He really was the loser after all.
Hope you got some sleep, hopefully took advantage of the extra hour.
And I agree about a SHL, make sure you are completely happy if you have one. If not, your homework this week Miss, is to get one.
Take care.