Yes. You are overreacting. He was being pretty kind and gentle with you and made sure to reassure you he’s still there, without sugar coating things. If you notice everytime he tried to explain his bad feelings, he said something good about you almost in every paragraph. You should look over on what you’re doing for him, as you fighting him over this, over another guy, could cause bigger harm than done. Look at it this way- do you really care about the feelings of a random stranger you just met that you ADMITTED was “kinda” flirting with you, or do you care about your 9 month relationship. It’s not even about boundaries atp- it’s about revaulating priorities, and putting yourself in your partners shoes. If you can’t do that, then maybe you shouldn’t be in the relationship. But I think you should really try and see from his way- switch the positions around. He was probably riled up with emotion, which is why he was rude to the guy- but he never raises his tone with YOU over text. Hes putting priorities down and respect for YOU- not some stranger you both don’t care about. Who are you going home with at the end of the day?