I think you were right to request the wellness check. Better safe than sorry. Left alone, as he was, anything could have happened to him. Clearly, he could not look after himself and should not have been left on his own.

His being moved to an assisted living facility sounds like what he needed. I hope it's a decent place. Some are better than others. Anything is better than him being in a house by himself.

I'm sorry you don't have family that are really family to you. It doesn't sound like that will ever change, which is sad. Sometimes you have to let go and accept that people are unlikely to change. Maybe they can't. We all need others in our lives. I hope you can find relationships that you will want to invest in. Some people you have to give up on.