I think he's done with you sweety
sorry but I see all those signs there.
He will cheat on you so you don't get mad? Sounds like he doesn't want to put any effort in amd wants it now too. He's being selfish. Poly doesn't work with the snap of your fingers and a bad attitude towards those you are supposidly in love with.
He might be almost thirty but he is way too self centered to know how to be a contributor to a healthy relationship it sounds like. In this way he is around 15. I know 15 year olds that are more mature.
It sounds like he's really frustrated and uninterested in participating in your relationship any more. It sounds like he just wants to break free and go fuck a whole bunch of women that he thinks will accept that. Wellllll, good luck to him. Thing is, to have something real in life one has to put in the time and effort. Has to put up with stuff that is frustrating and hard to navigate through.
If I were you I would back right off. Give him some space and tell him you will wait for him to talk and that you suggest he read here or get help elsewhere. When he wants to talk again about this then he will have to come to you and be prepared to work. Make sure he knows that you will not put up with cheating and that if he cheats in that time then you will leave him. To me that would be the bottom line.
You can do much better than be with a cheater. You have your self worth to think about and your integrity. If he wants to blow his because he is too lazy to work on his relationship that's his choice. Hopefully that is an empty threat. Threatening is bad enough but to go the route of cheating will mean ten times the work afterwards. He won't remember the sex five years from now, he will remember the deciet, greed, trauma he caused, and how he gave up his integrity for a fuck. I suggest you make sure that he is aware of that.
Backing off might give him the break he needs to figure out what he will do. I would make sure he knows that you won't just leave it though and will be asking him how its going within a day or two. If his answer is that he doesn't know yet, then leave it and walk away. The idea is to make sure he is on it, not to pester. Also perhaps to give you some peace of mind.
It kind of makes me wonder when you say you "like" him. What's that all about?