Can't believe I forgot to mention this:

My mom told me about my stepdad's reaction to the letter. He interpreted the letter in which I very honestly addressed my own struggles with anger, and my offer of compassion (though not a relationship) to him, as someone who can relate to his struggles, as an indication that I am "still very angry at [him]." That's all he took from it.

I told my mom to please convey to him that this wasn't the point of my letter at all, but more to be honest with him, to wish him the best, and to let him know that I feel ready to forgive what can't be changed. I was acknowledging his bitterness and saying to him, "you don't have to be bitter your whole life."

During a follow-up conversation he told her that why I am so upset is a mystery to him since it wasn't me he beat up but her, and later, my sister. He then asked if I was seeing a psychologist. When my mother told him I was, he quipped that instead of "wasting [my] money, [I] should turn to Jesus."

I think any responsibility I had to him in this situation has now been officially fulfilled.