Mom and Grandma hijacked our guest list

My FH and I wanted a small, intimate wedding since we don’t have a lot of close friends (65-70ish people we were hoping for). We both made this very clear to both of our parents. I made up a guest list of who we thought would definitely be invited and asked our mothers for input on who they’d want there. My mom and grandma decided to pay for our venue as our wedding present (unexpected but very generous). Next thing I know, my mom had added so many cousins of hers and my grandmas (whom either I’ve never met or hardly ever see) and when I told them I didn’t want these people added, I was met with “well this is just how it is and how you do things” and then was asked who WE could cut from our list which was already small to begin with (if we cut any of our friends, we’d literally have none of our own friends there). She then added four more on top of that who I told my grandma flat out I don’t want there because I’m not close to them. I’m being steamrolled.

Now FH and I are constantly arguing over me saying something to them to cut down their list. I’ve tried numerous times and I’m so tired of fighting this fight alone. I finally told him to speak up and say something to my mom to express his concern. On top of that, his mom is upset that her sister who she isn’t speaking to somehow found out about our engagement (we work for the same medical practice in different locations) and is now blaming me for this when I hadn’t said anything. I told him he isn’t obligated to invite anyone he or his parents don’t want there. I already got guff from my MIL about the 18+ rule.

I don’t know how to handle this mess and I don’t want to be the only one fighting for what WE want for our wedding but I feel I’m all alone in this. Since they’re paying for just the venue I know they have a little more say but he refuses to understand that. I’m already doing 80% of this planning by myself, I don’t know how much more stress I can take.