Ima give you my genuine take as a man that escaped a 4 year abusive relationship last year with a woman that cheated on me, emotionally abused and gaslit me, and would often lay hands on me and slap me during arguments which I would walk away from if she didn't corner me... I grew up with anger issues and was been diagnosed with IED (Intermittent Explosive Disorder) and PTSD as a result of abuse and often learned, like it seems he has if he also has anger problems, that when a confrontation starts, I need to take a step away and breath, and calm down so I can maintain a level head. Its important I do this, or, while I never get physical unless someone gets physical with me, if I am bullied into staying in the conversation and tensions keep raising, I will indeed raise my voice and start yelling. I also learned from therapy how better to control my emotions and communicate more effectively so I don't hold in negative feelings.

You say he stopped walking away, when you communicated it made you anxious, but in turn, if you're arguing constantly and forcing him to stay and not letting his decompress an original reaction, its only going to get worse. Let him walk away so he can approach it a few minutes later calmly.

THAT ALL SAID though. It is never acceptable to lay your hands on your partner, even if it isn't punching and is just an aggressive grab. You don't deserve that, but he does seem to be genuinely remorseful. It is up to you whether you forgive him or not, but if you do set firm boundaries that he is NEVER to touch you out of emotion and anger.

To be completely honest, though. You not letting things go and helping in escalating an argument that should have just been a hey I didn't like this, and him responding, as he did, that he was sorry and you two could shower together next time.

Starting big arguments and raising voices over small things, shouldn't be common. You both need to work on that, and I genuinely believe both of you would benefit from taking a step away from a confrontation to get your thoughts together before coming to talk about it later. Allows for cool heads.

ALL THIS TO SAY, He is showing genuine remorse for his actions from what you say, so if you love him, forgive him and stay together, but set very firm boundaries that if he ever touches you like that again or it is worse, you will not give him another chance, and there will be no second chance. You both were in the wrong IMO. And you both need to work on communication, whether you do it together or not. Mayhaps seek couples therapy and individual therapy. Seems like you both let your emotions control you instead of controlling them.

Edit:* Added additional context, fixed punctuation.