In these situations, I think it's important to see things from both sides. It's obvious you don't get on with your ex, so you each think the worst of each other's motives all the time. Are you beyond the stage where you can try to reach some kind of mutually acceptable agreement for his contact with the kids?
If it's true that previously you weren't allowing him to see one of the kids at all, I can understand some of where he's coming from, to be honest. If nothing else, you need your own behaviour to be beyond reproach here, so that if things do break down irretrievably, you'll be sure in your own mind that you've truly done what you can to try to resolve the situation at least for the sake of the kids if nothing else.
I think you should phone him - not text - and try to sort this out. I don't think there's anything wrong with admitting you need a break - he's still their father, and still has a responsibility to take on a share of the parenting regardless of the way he feels about you. Unless he's a complete bastard (always possible) a reasoned and fair approach from you is your best chance of getting him to co-operate.