I certainly empathize with you. My previous ex and I were open mostly due to long distance (but also to appease his much higher libido) and we had a handful of rules that were similar. To my knowledge he never outright broke any of them but he definitely stretched, e.g. we agreed to keep everything we did out of our individual beds and then he had someone in his room but on a chair and the floor. The intent of that rule was to keep certain spaces to just us and he knew that, but went ahead anyway.

You mention that he says something like "I need this" which is a bit of a flag as it's somewhat emotionally abusive. What he's saying there is "my needs are more important than yours, and they need to be filled regardless of how you feel about it".

To compare to another situation with my ex, early on he was mildly upset with me for playing around with a guy in the middle of a week, then properly hooking up with him that weekend. Not wanting to make him unhappy or uncomfortable, I told him I'd try not to do that again and definitely consult him if it ever came up. On the other side of things, only a short while after that he had two guys over to his place back-to-back, one of which he flipped with multiple times. When I expressed my own discomfort which was magnified by his own feelings about me going twice in one week, he expressed a similar sentiment of "I've had a rough week and I needed it."

Ultimately what you really have to watch out for is a flippancy. When I finally had it out with my ex about the double standards and how upset I was getting he said something to the extent of "I only do things that might upset you if I know you'll get over it." Something like that makes it clear that a partner is far more concerned with himself and doesn't actually care much about how you feel. I'm not saying this is necessarily the case with your guy, but it's something to think about.

I don't think you should go breaking up over this, but I think you need to sit him down and make it clear to him how you feel. An open arrangement takes a lot of work, communication, and trust; some would argue moreso than a monogamous relationship. It doesn't matter if it's a small rule, the reason you're upset is because the two of you worked out boundaries/conditions that were comfortable/agreeable and he violated that.