Just need support

[Ahoy]

Do you have a guest bedroom where you could sleep? A basement room? A sofa? You taking the initiative to sleep elsewhere will be setting a kind of boundary: You're not willing to continue to pretend that everything is okay when she is likely stepping out on you. If you are meeting her emotional needs, now is the time to draw back. This will be much easier when you're not under the same roof.

For example, my H wanted me to come to the door when dropping off D14 at his place so that she could see us "chat in a friendly way." I thought that was a farce, but instead of saying so outright (and instead of telling him that I wasn't interested in being friends while he has a girlfriend on the side, which he admitted to our daughter), I told him I needed some space -- the same line he had given me previously at BD.
I no longer went out to dinner with him and pretended to all be a happy family. That was not to anyone's benefit except his. It just confused my daughter, and these invitations were all about meeting his needs -- his need to seem like a good guy, his need to ask me for favors, his need for my attention.

So ask yourself: what is your wife asking of you that is entirely for her benefit? There is where you can pull back and set boundaries. Don't be afraid. You can do it.