Just my 2 cents....What it sounds like you are proposing is more of an ultimatum than a boundary. If H does x, then he can have Y. If you read through these boards, especially the vets in MLC, a boundary is put in place to protect you and not to achieve a given result. To take it a step further, the most successful boundaries are the ones that are put up without telling the other person a thing about them.
You have boundaries....Your problem has been putting them into affect, so they are basically useless. You H has basically free run to show up at your house and get family time as his schedule allows. Now I do agree that family time is important, but there hasn't been a line drawn in the sand. So in essence, your H gets his family time with you and the boys at HIS schedule while getting his fun time with the OW. So this limbo is in reality of your making. You haven't taken away unfettered family time even though you know fun time is with the OW.
If you decide to get out of the game, start accepting the reality of your separation, and draw that line in the sand....Then his limbo will become more defined without an ultimatum. He will have to look at his life and decide what is important to him. You don't control his choice (in affect what your IC proposed) but you do control yourself.
The harsh reality is....if things keep going the way they are in the future he will not be able to show up whenever he wants. He will need to get the boys, take them to his place, and spend time with them. Maybe still a game night or something, but not hanging out at 3B's place....as that is your place. That is a result of his choice, not yours.....but right now he doesn't have to deal with that choice because you haven't enforced your boundaries....Which he has no need to know of....They are your boundaries.
