Having followed you posts since April, this seems the best outcome for you. You have been admirable in the length and depth of your compassion for him, but as you have related he has chosen not to pursue therapy options that have potential to improve both his functioning and your relationship.

My guess is one of the reasons you feel alone is that you are in fact, at home, emotionally alone. Hopefully the therapist and groups that you are in can help alleviate this. It’s possible to be alone and not lonely, whereas now it sounds as if you are not physically alone yet lonely. Consider if you do go forward, if building a house on the lot next door gives you enough space.

Wishing you happiness as this works itself through.