A lot of us are. I was lucky enough to get the sole custody, but it doesn't change the issues, just gives me a little more rope.
Here are some tips: - Joint custody still means that there is a tie breaker. Talk to your attorney and see what your state's feel is on that issue. I was told that in a joint situation, the residential parent is the tie breaker. - Work with a counselor on boundaries. You can't control him, but you can control you. - Limit contact to email and certain times of week. That keeps it under a boundary for you that lets the rest of the week be calmer.
It is hard, but live exactly to the agreement. Flexibility is earned, not automatic and if you live to that, then you can ignore the rantings. Your kids will appreciate what they can count on. It will get better - never normal and non-adversarial, but it will get better.
Your battles need to de-escalate. You can't stop him from anything, but if you refuse to fight, it will be better for your kids.