OK I reread this and I am seeing things a bit differently now.
Do I condone his behavior? No.
Is this a toxic relationship? Yes
Should you leave? I'm gonna say yes because you are unhappy and it seems like your relationship has gone past the point of no return.
But is it your fault?...Yes and No....also can't accurately say as don't have all the facts.
Abuse is NOT your fault. and hasn't gotten any better by this time is unlikely to change. To that point he is most definitely at fault for his treatment of you. Nobody deserves this.
You admit to fessing up to your mistakes and issues. And he chose to stay to forgive...but it is easy to say you forgive someone you love...harder to get to the point of full forgiveness.
My point is this: You did wrong..you have your reasons and justifications..you admitted to your faults and mistakes..he loves/d you so..he decided to (try) forgive you. This is only the first step of forgiveness. Most relationships get here...but what happens next is key!... When you fond out thst someone you trusted lied to you, hid stuff from you..this obviously is going to cause mistrust and all the horrible feelings that go along with it.
If he wasn't verbally or emotionally abusive before you told him this..then it is unlikely that he was purposefully or maliciously using it against you.
What did you do next? Do you feel like you truly did everything possible to regain his trust and understand that some residual anger/hurt on his part was normal? In the days and months following how did you respond to his feelings? Did you get defensive? or did you go spineless and just take it either with silence or begging and groveling?..Or did you truly make an effort to work through it WITH him from an honest place of love...not just personal redemption?
There is a give and take that needs to occur at this stage....
Not all people process things the same or at the same rate...
Communication styles different as well...
If you are the one who caused the break in trust then it more heavily relies on you to do the majority of the heavy lifting to try to repair that trust.
First off..Never assume another is automatically going to be able to really know what they need in order to put the past behind fully; much less be able to clearly express this...
As the initial wrongdoer. ...it is your job to be patient, kind , understanding, and initiate open communication in a very clear way. Ask them if they are ok?...well a lot of people will automatically answer fine...even when not.
So you have to be clearer..
You have a conversation. It's called GIVE.
Gentle manner
Interested and in tuned body language/listening skills
Validating feelings concerns and needs of others
Expressing your understanding and your concerns and needs as well...
Then you let them know what you are willing to do to preserve the relationship and what you need from them to help you fix the problem together.
And then you do everything in your power to actually do it!
But you hold them to their end as well.

I wish I could say I am this skillful, but no just schooled in DBT..not anywhere near the point of mastery.

Progress maybe slower than you would like but as long as there is progress you keep your word and keep communicating...

If you feel that to the best of your ability that in the aftermath you gave it your true best effort and as skillfully as possible from a true place of love have him every opportunity to do the same...and he just couldn't get past it. Well then at that point you could say you were no longer at fault...then it is his problem and he is now at fault for not holding up his end.

The notion that he drove you to go outside the bounds of your relationship...I'm sorry but that is ridiculous.

You control your actions!! Even if he is not controlling his own....he has his issues you have yours. He was not able to see or accept his issues and it was at the point where you couldn't take anymore. Then YOU LEAVE!!..even if just for a bit of breathing room and contemplation....

My assessment BOTH parties are guilty of not being COMPLETELY HONEST WITH SELF OR THEIR PARTNER.

Now I am aware that I just gave you a bit of a harsh lashing...Please do not misunderstand! I am not taking his side or saying he is In ANY WAY JUSTIFIED IN HIS TREATMENT OF YOU!! ABSOLUTELY NOT!...I don't not know if he is truly just an abusive person by nature....or just needs to do some more introspective work on himself before he is mature enough to be in a healthy relationship...But ABUSE is ABUSE. He had no right to EVER treat you that way.

But going forward, you also appear to have a lot of introspective work to do on yourself before you are ready to be in a healthy relationship as well.
I spent years banging my head off a wall trying to figure out any and every possible way to get through to someone who was not able to admit, accept, or even give more than a few days showing of effort to help repair and strengthen our relationship. And I am no where near perfect...I got issues all over the place...and like your relationship you the end it was nothing but arguing.. complete stand still...I allowed him to make me believe I was completely unfounded in my feeling and just psych crazy woman...and I know the deep scars that leaves and how whether or not the others intentions were malicious or just shortsightedly selfish...that you get to the point where the their view of you becomes your reality...and you look at the way you acted and feel like the worst person ever..because you realise that you are behaving exactly how they conditioned you to behave. ..I'm in a similar place as you right now...hopefully we both will be able to break the cycle and truly heal and thrive
~S♡☆(lost)