You don't have any boundaries. You just keep trying to think you have boundaries but if you did, you wouldn't be going through any of this. A boundary shouldn't be allowed to be crossed. So didn't you have a boundary regarding a cheating husband? When he cheated, he crossed that boundary, but all you did about it was to add another boundary, or rather you added an ultimatum. He found a way to get around that one and is well on his way to getting away with it because there you are arguing with him, questioning him, bewildered, issuing ultimatums, and don't know what to do.
Either you have boundaries or you don't have boundaries. If you had any regarding a cheating husband, it would have been "I will not tolerate my husband cheating on me and if he does, I will leave him." If that wasn't your boundary, then you didn't have one regarding a cheating husband. If that was your boundary, or rather what you thought was your boundary, there would not be anything to follow except you leaving. Instead, you kept pushing out new boundaries for him to cross, and he keeps crossing them. And you still aren't doing anything.
Stop thinking you have any boundaries because you don't. All you have is a cheating husband and no idea what to do about it because you're too afraid to do the one and only thing you should be doing.
If you cannot live up to what you call boundaries and cannot live up to your ultimatums, then stop making them. You don't want to leave your husband, so you're just wasting your own time with hurt feelings and aggravation and all this back and forth stuff. He's a liar and a cheat. That's all there is to know and all you need to know. If you're not going to do anything about it, you might as well be quiet and let him do whatever he wants since you at least get to keep him.