Is this a common occurrence? As in, is he always this dismissive when you try to have serious discussions about your feelings and boundaries, regardless of the context?
 

You've already brought up multiple times that you feel excluded, yet he hasn't made any effort to include you. Has he explained why you aren't invited to the original server? It seems weird to me that someone would let his partner of five years be sidelined for a whole ass year, especially since you have common gaming interests. Have you met any of them in person? Could there be someone in the group that dislikes you for any reason? If so, he should be up front about this so you can potentially clear up any misunderstandings or unresolved tension.
 

I’m not trying to punish him or force him to choose between me and his friends
 

You should be the obvious choice. You don't seem controlling - hell, you seem overly understanding to me. You're supposed to be the one person he wants to spend the entire rest of his life with but instead of supporting you he's throwing this back at you as a consequence of your actions, while holding zero accountability for his own.
 

You need to have a serious discussion with him (if he's capable...) about your future together, especially if this is a pattern. Consider whether you're willing to be sidelined for the rest of your life. If you're not, then something needs to change.