Well that’s all quite difficult.
Assuming if he doesn’t go, no one else can fill in for him and the group can’t do what they are doing I would expect him to not be able to just leave a practice or try and plan round it.
I am assuming they can’t perform unless he is there because he cancelled the whole groups attendance based on your holiday. My Dad actually did morris dancing and that’s not how his group ran. People, even leaders, would miss for all sorts of reasons but others could carry on.
But of course people are going to annoyed if they plan on attending something then they can’t because it no longer suits one person. Expecting people to be perfectly happy to change plans because it doesn’t suit one person, is unrealistic.
He didn’t put the hobby in front of the wedding. I don’t get the issue with asking a neighbour to check. I have a 20 year old dd and 13 year old ds. I would do the same. Especially if a session couldn’t continue without me. Not sure why you nearly left him over that one.
If he was that upset he was missing trick or treating, I don’t believe he could have made different arrangements for the following year.
It might be the connection to his ex wife that’s bothering you. It could be that you feel resentful that the group aren’t happy to change plans for things you feel are important and that puts you off them. Maybe you feel it shouldn’t be set up in such a way it can’t go ahead without him because that puts pressure on you.
But I don’t think any of your examples are as awful as you believe them. Only you can figure out where your feelings are coming from.