I know you said your husband communicatest with the ex, maybe not appeases her, but I think this will still touch on something with you, and maybe a few others here:

Saying Yes to the Ex
6 Reasons He Instinctively Says Yes When You Want Him to Say No!
by JENNA KORF

Do you hate it when your husband’s
difficult ex asks for something and your husband jumps on the yes wagon? Or, even worse, when she wants something seemingly unreasonable— and even though you can tell from a mile away that he’ll regret it—he complies? You’re probably wondering, why on earth is he still being kind to her? Why is he still doing things for her after the way she treats him? Well, you might be surprised to learn that, in most cases, men are not being wimpy or spineless. They’re being driven by their instincts.

Here are six possible reasons your husband says yes to his ex when you think he should be saying no:

⊲ TO PROTECT YOU. I know it seems counterintuitive and you don’t feel protected, but your husband has been dealing with her for years and really wants to keep the conflict out of your house and away from you. His way of doing that is to pacify her. Giving in to her may seem like no big deal to him because in his mind it is well worth it if he can keep her wrath away from you.

⊲ HE DOESN’T THINK HE CAN WIN. Alison Armstrong, designer of the widely acclaimed Celebrating Men, Satisfying Women® workshop, states that if men don’t think they have a 90 to 95 percent chance of winning something or succeeding, they won’t even try. It’s their instinct to conserve their energy for wins. This means if he has a history of losing court battles or being involved in long, drawn out conflicts with no resolution, he might just be too emotionally exhausted to bother. To him, it’s just easier to say yes.

⊲ IT’S HIS INSTINCT TO PROVIDE FOR HER. Yikes! Ouch! What?! Yes, I know, this is a hard one to hear. But it’s the truth. This is one of those instincts that may be misguided because it’s in direct conflict with protecting and providing for you, but nevertheless it may exist. Women often have trouble understanding this because we don’t have the same instincts as men. We have an especially hard time understanding this if the ex has been high conflict, participating in alienating the kids from their father, engaging in court battles, harassment and other behavior that, as women, we would never tolerate. But a man’s instinct to provide and protect is there for the survival of the species. It doesn’t just go away because someone might not deserve it.

⊲ IT’S A HABIT. In some cases, it really is that simple. Seriously, after a man has been providing for a woman for so long, it can be a really hard habit to break. It’s very similar to his and his ex’s dysfunctional habit of fighting, which you’ve probably witnessed. That dynamic can take years to change or undo.
⊲ HE FEELS THAT HE’S PROVIDING FOR HIS KIDS THROUGH HER. He may be willing to do something she requested or demanded if he thinks it will benefit the kids. This benefit may be direct in that what she’s asking actu- ally is better for the kids. Or it could be indi- rect in that by simply avoiding conflict with her he is protecting them.

⊲ HE’S AFRAID OF LOSING HIS KIDS. This is a very real and valid fear that some fathers have. Moms hold a lot of power, and it’s easy for us as stepmoms to want our men to fight for their rights instead of giving in. But he may not feel compelled to do this (refer to No.
2) or he may not be financially able to fight for his kids, if it should come to that.

So, What’s a Wife to Do?
Stop calling him a wimp and stop giving him a hard time every time he says yes to her. When you complain, all he hears is criticism, which only serves to create or perpetuate conflict between you two. It doesn’t compel him to change his behavior. He sees your complaints as his failure to make you happy, which causes a large amount of shame and discomfort in him, resulting in his shutting down.

Recognize that it usually takes a big violation on the ex’s part, something that he considers unforgiveable, to get him to start saying no to her. This is something he has to learn and experience on his own. It’s not something you can convince him of or push him into.

Brush up on your communication skills and learn how to make requests, not demands. You’ll have a much better chance of him being receptive to your request if he doesn’t feel criticized or bullied. An example of this would be “Honey, I know you had a good reason for agreeing to x, but I feel really anxious about y, so next time do you think we can look into some other potential solutions?”

Remember that he’s mostly functioning from instinct, which is hard as hell to temper. Try to appreciate his intentions and know that he ultimately wants you to be happy, which means protecting you from something he’s had to deal with for way too long.