I'm so sorry you are feeling so frustratetd.
And I do understand that in situations like this, it's often the principle of the matter. At least that's how it is for us. It seems to me that if she needs to revise the visitation schedule for her new job, then the schedule should be revised, but to call it "her time" with him isn't exactly accurate, even if she does think of it as him being "babysat" by dad.
mammastar2, that's so great that your DH and his ex had that agreement! I think that would be the ideal. But realistically, that never would have worked for us and it might not work for lots of other families. In our situation, my DH's ex is all about who owes her what, never about what she owes to anyone. And it's always been that way. It's all about her. At least when it comes to DSS and to us, which is all I can really judge her on since I don't know her in any other context.
For example, DSS is 13 and lived with her until about a year ago. During that time, we paid hefty child support (no issue doing it at all!) and DH had it set up through online bill pay so that each pay day, a check would automatically go out to her. Obviously, the check would not go out until the money was in the account, so it would usually arrive to her a couple of days after the "due dates" of the 1st and 15th, which was only in her mind, not in any documentation. Without fail, almost every single month, she would call at least once, usually twice to ask where the CS was and ask why he was dragging his feet sending it. He would explain to her (again!) how the bank send the check and she should have it any day. But she refused to just let that ride and had to hassle him about the check being 2 days "late".
Fast forward to now - DSS has been living with us for over a year. She pays minimal CS (a small, small fraction of what we paid to her - again this is fine and fair in our opinion) which she agreed to pay around the 1st of each month. So far, she has never once paid the CS within the first half of the month, muchless around the 1st! DH is tired of reminding her, so he stopped last month. Never did see and CS in Sept and so far none in Oct. If she didn't get any money for that long, she would be calling here every day about it!
So anyway, that's just a current example of how she takes advantage of us, but expects perfection in return. There are hundreds more examples I could give, but I won't. The point is, not every one in these situations is mature enough to handle an arrangement like the one your DH and his ex have going on. And I do think sometimes it's better if it's more cut and dried and consistent.
MomBirthmomStepmom - any way she would be open to revising the schedule again? If she needs to work, she needs to work. But that doesn't mean she shouldn't be seeing her child when she can. Hope you guys can work something out that is better for everyone. Let us know how it goes.