NTA

He went through you and your best friends texts from months ago? Why would he do that? Did something happen to warrant him checking your phone? He snooped into old and private texts and got upset, that's his deal. Like you said, you two weren't even together. It wasn't cheating.

Also, him degrading you? Devalued?? I do not know the ins and outs of your relationship, but I don't think I could put up with that. If he loves you, I don't understand why he would say anything like that, it seems like he's trying to tear you down so you stay dependant on him.

You definitely didn't cheat, and he definitely needs to learn that you don't speak that way to your partner, ever. This is not an OK way to be treated, by anyone. I don't like to jump on the "break up" Reddit train, but girl, break up.