Okay, I am going to play devil's advocate here. Some married or long-term couples come into poly through not-so-honest means, which means when they decide to try it honestly, there are already trust issues. As the new person in a relationship with one of them, that's totally not your fault. It does, however, mean that things typically go slower. That's what we had to do, go slow, with lots of communication.
However, it was never that bf's needs and wants didn't matter. As a matter of fact, as we were talking as friends first, he knew some of the past issues. When he brought up dating, he wanted to know how we both felt about it.
So we moved slow, but hubby, whose trust had been broken, made a point of asking himself how he would want to be treated if he was in bf's shoes, remembering that the trust we were rebuilding was between us, and not about bf, but about how I handled NRE.
The things you list are just controlling and inappropriate in any relationship. My hubby doesn't get a thank you for 'sharing' me. If anything, he's the one that enjoys that there is someone else he commiserate with on how I don't like to wear clothes around the house. While we have check-ins, and emergencies with kids come first, that's something that we all agree to, and it isn't abused. If a kid has the flu or is throwing up, hubby can handle it without me. A hospital trip, I better get a call about.
The first overnight was something we geared up for, but there was no veto. I know a lot of marriages just opening will do the veto power. I'm not saying it's right, but sometimes it's a safety net the other partner has to sort of remind themselves that they are not disposable. We had one, but it was pretty much a Catch-22. If he felt the need to use it, then there were problems that using it wouldn't fix. He could use it freely now (according to bf and me) and he sees no need to. In the end, it's a crutch that the couple learns is not helpful at all. So I won't say never use one, but understand it's a crutch, and should be a short-term one.
Three years is so not short term, even in comparison to relationships in the double digits!
The best recourse is to sit down all three of you and explain that since this involves all three of you, all three of you should be heard and respected. It's not fair for any ONE of you to hold up or hold hostage someone else's relationship. Working together, you can help each other with things that are scary or uncomfortable, but controlling someone else won't help anyone and will just cause a cycle that will continue, with or without you there.