Future FIL-zilla? I need to vent

I think I mostly need to vent at this point, but I am completely overwhelmed with how awful my fiance's father has been acting the past couple of weeks. For context, he is paying for half the wedding and my parents are paying for the other half. We proposed a reasonable budget (that I feel confident we will stick to), and said that anything extra we are more than happy to cover ourselves.

The thing is, I don't particularly want a big wedding, but he has a big loving family, and as much as I would love to elope my fiance talked me into a 100 person wedding (and I actually was starting to get excited about the idea). But I have a somewhat low tolerance for dramatics and bullshit behavior, and I am rapidly approaching my limit.

It started out fine, I was happy to listen to his ideas and make him feel included. I am fully willing to let him dictate the guest list (as long as we don't go over 120 people since that would really wreck the budget). He mentioned that he would like us to check out his country club (which is not at all my or my fiances style). We looked into it to make him happy, but we found a venue of a similar pricing that is perfect.

We offered for him to come tour with us, but he declined. Before we put down the non-refundable deposit (with my parents money), we called and had him confirm that he was okay with it and not offended that we weren't going to use the country club. He seemed fine and gave the go-ahead.

All of the sudden, he seems to have changed his mind. He keeps contacting my fiance and saying that he doesn't think the caterers are good, or that they are overpriced (including a weird theory that the venue is so cheap because they are getting kick-backs from the caterers). But we already budgeted, so this is not an issue. He will not listen, and even went out of his way to call my fiance and tell him he contacted his club about scheduling the wedding there and forwarded the email with details!

It feels like he has not listened to a damn thing we have said. And again, I never wanted to have a big ceremony! And if I'm going to be treated like this, I am ready to cancel and just have a court house wedding. I understand that with giving the money comes a certain amount of input, but it feels like he is ignoring us and planning a whole other ceremony behind my back and I find that unacceptable.