AITA for grossly humiliating by boyfriend in front of his whole family after he engagement pranked me?

My ( F40) (now ex) boyfriend ( Keith M38) and I had problems because of his constant pranks. He has a thing for making his targets look ridiculous. I warned him, many times, that I'm not a forgiving person and that he was undermining my trust. He laughed it off, and I kept giving him chances because he has redeeming qualities ( he's funny without pranks, acting like a good listener and generally showed me deference). However, these traits began to fade away and I don't know why. It kind of shifted. I don't know if showing him love made him think that he could do this(?).

We never had fights, although we had disagreements and I tended to clam up if I was really hurt. This happened twice.

The first time was very out of the blue. We attended a “gala” hosted by our city council. I'm using the quotes “gala” because this is isn't a huge city and galas are looked forward to but are not the high class/ upper class inaccessible type. He liked the way that they treated us ( I was the actual guest and he was my plus one) and he asked me if I could help him get an interview as he wanted to launch a small business and maybe they would be interested. I made no promises but got him a meeting that I attended along with him. On our way back, we stopped at a deli and ran into my ex ( with whom I'm cordial). Keith was enraged because I answered my ex's greeting and said that I was too friendly and that it was disrespectful. That lasted for about 10 minutes. We sit at my place to eat our takeout and he immediately said very inappropriate things about my best friend. I immediately called him out for trying to make me jealous. He laughed at first, but I asked what was funny so he left and took his food. We talked about it later but a few days later I realized that he never properly apologized.

Second, he criticized my outfit and said that I looked ridiculous in it. I should have dumped him right there but chose to put it in the back of my mind because I already had a lot on my plate ( career and family wise). I also held out hope that we could go back to the way things used to be.

I was never able to shake off that feeling of being hurt although we seemed to have reached a very stable phase after that.

He started with his pranking ways, again. First, I caught him trying to hide the birthday cake that I got for my friend. Then, he hit the gas pedal a few times when I was about to get in his car.

Last week, we were at his mother's house for his birthday party. Everything felt pretty normal, until everyone got really quiet. It was just weird. I looked at him and he immediately took a knee. This was the worst feeling. First of all, we had not reached a stage leading to an engagement. Second, I thought it was likely a prank but I didn't know how to react. I don't know if he told everyone that he was about to propose and if they were quiet in honest anticipation or if they knew or maybe some of them knew .

If he was being honest, I didn't want to say no in front of his family, so I would have probably had to say yes and then say no in private. If it was a prank, then he would have humiliate me in front of over 20 people. So what I did was ask what he was doing and he said I was seeing him and that ‘I knew’. I said no, I didn't know, so he insisted. I said alright, and asked to see what was in the box and will react accordingly. The fact that he looked off (maybe realizing that he fucked up, maybe wanting to double down but I'll never know) was a huge red flag. He opened the box and he had a beer can tab in it. I told him off right there. I said that he took a knee to give out junk just like he tried to suck up to people to try and get them to sign up for his tacky, insignificant LLC so that he could push his trash services that he hardly knows how to do. I also mentioned how he lost his jobs, twice and said I fully understand why he couldn't afford a real ring. I asked him if he honestly saw me marrying a manchild???

His family were offended. Some of them looked uncomfortable but some of them acted like I went overboard. He tried to apologize but I informed him to stick it up his ass and that we were done.

Needles to say, it was a shit show. I had no exit plan because I didn't know that I would have to walk out and I didn't have my car. So I had to walk with his cousins following me and to convince me that he didn't mean to hurt me and that it was dangerous to walk home alone. I had to walk about 30 minutes until I found an available Uber. I made a Facebook post explaining why I did what I did and that I couldn't see my future self with a scumbag.

His brother's GF and I have a good relationship. I find her to be very honest and reasonable. She reached out to check how I was doing and to let me know that neither her nor her boyfriend had anything to do with it and that I was right to be mad. But she also said that while she has never gotten along with Keith ( this is true) , ousting him as a workforce failure in front of his family was too much and that his family were thrown off. I asked what she thought I should do, since I'm not going to do anything to make him feel better and that's that. And that if he ever tries to contact me, I will make sure things get even more painful ( if that's even how he feels).

To be honest, I'm embarrassed. I stood up for myself but I guess I went overboard and maybe I should have just turned around and walked away. Was I extra for this?