stand your ground - you really really really have to. If you let him weasel you around on this one, you're just demonstrating to him that it works, that you're willing to be manipulated, and that your own boundaries don't matter.
Don't be afraid of him calling you controlling. I sense you have a lot of fear around that. If I can smell it, he can, and he will use it.
You are not trying to control him. He is free to do precisely what he wants. You are telling him you won't go on the trip under certain circumstances.
He has no right at all to pout, to write little moany notes, to try to put this on you. You were very clear you didn't want to go on the trip unless you felt you could trust him. He's not willing to take the transparency actions that would help you trust him. He is choosing this, not you.
He WANTS her to be able to get in touch with him. He wants to leave that door open. He wants to have his cake and eat it, even as he has been ignoring your boundaries and planning a trip you've said you don't want.
During the SSM, he could have left you. He chose not to. He has a contribution to that situation and the SSM doesn't mean you owe him an open relationship and mindless obedience now.
I think for the your own self respect and the health of any future relationship you have with him, you have to stick to your guns. Say as little as possible now. You've been very clear and the ball is in his court so leave it there. Every single time you have a conversation about this, he is trying to give you back the ball and you have to make all this effort to leave it with him. Just refuse the conversations. 'You know what my decision is on this. You are free to do whatever you want. Because you are a liar and because you don't want to be transparent about blocking her, I have decided not to go on the trip.' That's it. Over and over again like a broken record. Nothing else.
He will try ALL the channels, May. Fasten your seatbelt.
