I too have struggled with ruminating over past regrets, shame and finding a way to forgive myself.
I can imagine if a good friend confessed his/her transgressions to you that you would have an easier time loving, accepting, and comforting them through those emotions. For some reason it's hard to offer the same kindness and understanding towards ourselves. It's as if we believe we need to punish ourselves by continually reminding ourselves of how we could have done so much better at the time. The past is there and will stay there.
I have read quite a bit of your story and I have gathered that where you were emotionally, mentally, physically and spiritually were the driving forces to motivate you getting sober and redefining the healthy thriving version that was inside you all along. You wouldn't make those choices now because you have grown into the person you were meant to be. Maybe in helping others here on SR and building a healthy life for yourself - you are doing just that, repairing the shame and little by little you will be able to forgive yourself.
Being unable to forgive yourself is a heavy burden to carry around. I suspect for most of us here on SR that the act of unburdening ourselves is part of the journey in being and staying sober.
Who you were and who you are now are worlds apart.