Sounds like you're in your head about it. A mental block never helps for a man or a woman when trying to climax. It sounds like you need to have an emotional connection in order to enjoy yourself properly. I would suggest seeing a therapist and having them help you through the mental block. Your ex really fucked you up and it's worth it to talk to someone.

If you got called a cunt for watching a show without her, you're in for a hell of a ride.

My wife and I talk about shows and whether we're going to watch together. You didn't but being called a cunt for it is a little overboard.

The conversation after is extremely important. Make sure you talk about how you felt about it, if any boundaries were crossed, if you want to continue, etc. Communication and trust are key.

That's up to you. I'm in an open marriage and that is something that my wife and I are both into but that sort of thing requires both people to be onboard and desiring it. If you don't want to do it, don't. It's really as simple as that.

If you decide it is something you'd like to do, make sure you have some long conversations about boundaries. Hopefully he's not using it as a way to get to sleep with other women as well.

Tread carefully and only do what you want to do.