Deep Disappointment – what now?

I have experienced a very deep disappointment from my father, with whom I have a very difficult relationship to start with. I have done a lot of work on this and I thought I was in a good place, but yesterday my father did something very hurtful, all while my mother (who hasn’t been with him in years) is dying. I am usually able to deal with him being hurtful by simply saying that this is how he is and not taking it personally. But with the context of my mom dying, and I am devastated and feel very alone.

I know the disappointment is based on my expectations of him. But I don’t think my expectation of him supporting me while my mother is dying is too much. This is more like he has shown me who he truly is, and I need to deal with it one way or another. So my question is, what now? Is Scholars saying that we need to accept everyone how they are, not expect anything from them, and continue to let them behave in hurtful ways?
Please clarify the point or maybe show me how I could use a model in this instance?