Your former spouse is inconsistent.. dumping the kids (and putting them in the middle) when it suits her and having no flexibility when you have a conflict of interest.
With your son's camp, perhaps you can find a counselor who'll stay with him for a fee til your daughter/former spouse can pick him up. Or going to a friend's house who's at camp those two days might work.
Document the conversations, the instances of her abuse toward you and the kids and hand it over to your lawyer.
Nothing you do or say will change her behavior. Give it to your lawyer.
If your former spouse wigs out anymore, I vote for getting her a toupee.
