Most Helpful Guy
Leave. Just leave. You've been married before so you should know the signs and this is a bloody big red flag. Get out
Most Helpful Girl
When someone is fooling around with the break-up threats it's because it's learned behaviour and they do not properly know how to handle stress. They use it to get your attention, and look at you - it works every time, every day. He tells you it's over and you jump to attention. Do you want to go through this for the rest of your life, or do you want to communicate to him that this sort of threat is not called for, nor is it solving anything.
In order to do this "reverse psychology" you have to prepare yourself for the worst, which is that your words will trigger him to actually end it. If you are fine with that, then maybe it should end. But if you are using this tactic as a game to show him how it feels, it does not sound like a mature relationship to be in. He definitely needs to understand that this isn't how married couples are to communicate and solve problems, and you should get it out of your head right now that tit-for-tat will only teach him that this is exactly how you both are going to get through tough times.
You deserve much more than someone being snappy with you every day. He is getting away with this behaviour and that is why every day you are dealing with it. Be the woman he loves, and show him that you want to move in to the next level of your relationship doing things differently - without his family's influence. Because right now, *you both* are your own family and need to be the core of everything to each other whether you get married and have kids or not.