I’m still so lost

[SteveLW]

The biggest thing I feel you need to stop doing is apologizing for the past. Next time he starts one of these talks just listen and validate. If he get frustrated and says something about you not being sorry, a simple statement like "I've already expressed remorse about the past, I cannot continue to apologize for things I've already said I was sorry about."

Let him know they you've apologized and are now ready to move forward, once and for all, and then go back to listening and validation.

We humans are funny creatures. We think that the more we apologize the more likely someone is to forgive us. Usually the exact opposite is the case. Each time they bring it up and you still continue to profusely apologize, it gives them their endorphin hit about how right they are. When you stop apologizing you short circuit their endorphin hit. And without that they are no longer incentivized to constantly rehash it. It also shows them that though you are remorseful, you've already apologized for the past, and that now you are moving forward from it. And so should they.

tldr; people will either forgive or they, so apologizing for the same things over and over again.