It honestly seems that you two have unusual amount of problems and fights and issues for a very new marriage. This is absolutely not typical.

You blame yourself for this. Even though it’s good that you don’t accept victim role and take responsibility for some issues, I am sure it’s not all you. I am absolutely sure it’s not just you. So you shaping up will just make you more of a doormat. It won’t change who he is

I kind of agree with una that your husband is who he is and you are who you are. If you two were 20, I’d suggest that you can still change as people. But not in fully developed age. You “made” him to give up who he is, guy who watches porn etc why would you marry someone who needs to be “made” into doing anything? You feel insecure because you married someone who likes flirting and porn and who knows what else and you made him stop, but you can’t fully trust him because deep inside you know who he is. Someone who needs to be made into a fully monogamous person, against his nature. You’ll never 100% trust him and not because of your trust issues. Because of who he is.

You only have two options. Accept that he is who he is and that’s how your marriage will always be. Fights and him being nasty unless you “shape up”. Or you can leave.

You can’t change him. It’s just not a valid option. If you wanted someone more financially responsible, more honest, less secretive, less flirty, not angry and argumentative, more ambitious, more thoughtful etc you’d have to marry a different man. It is what it is