My best friend, M (26F) has been dating J (26M) for about 10 months. I have never been a huge fan of J, but I've tried my best to get to know him and try to like him but it's just not working and now I feel like I finally know why. On Saturday, we did a beach day with M, J, Myself and L (26F) along with some of their other friends and J's parents. L & I went over to M&J's house before the beach to carpool together. Before we had gotten there, J had gone through M's phone and he found a snapchat from a guy from before they even knew each other. M has mentioned to me in the past that J does not like to talk about their past, especially hers because he feels insecure.
The day goes on and J does not speech to M. M finally tells us that all day whenever it's just been M&J he's been telling her how disgusting she is for talking to other men before they met. This started at the house in the morning and it's now 1 pm and she's finally telling us. We were all shocked that that was happening, I've asked if this has been happening before and she tells me "yes". A lot of the time it is unprovoked as well. J will apologize, M will forgive and J keeps on doing it.
We go over to a beach bar that's connected to the beach, we're all hanging out drinking at the pool there. We're ready to head back to the beach and watch the sunset. J opens the pool gate for M, M declines and says you go first after how he's been to her all day. J insists that he's just opening the door for her and to walk through as he's doing that, J says "You're disgusting". M is very clearly upset at this point and we're all able to tell something is going on with them.
Finally, we're all ready to leave. J has purposefully ignored M all day. We're otw back and J says "home is 26 miles home, I have 38 miles to empty, I'm just gonna get gas later". M says "Actually, I really have to pee, can you please pull over?" J does not acknowledge it. I didn't think much of this because, who wouldn't let someone else pee? 10 minutes goes by and we've passed plenty of gas stations for us to stop. I text in mine, M & L's group chat and I asked "is he going to let you pee?" she texts back and says no. So I asked again to please pull over to pee because I was about to pee myself (I didn't have to pee). He goes oh ya of course, let me just pull in. J pulls into the gas station and you can tell his is PISSED. We go to the bathroom all is fine.
This is all clearly abusive, right? How do I go about telling her this is? I know abusive is a heavy word but I'm genuinely worried, they haven't even been together a year and there's so many red flags.
TL;DR: My bestie's boyfriend wouldn't let her pee, isn't that a form of abuse? What do I do?