Sorry this is happening, but you cannot get the two of them to do anything, you cannot get him to not be in a certain mood or to be in a good one, nor can you walk on eggshells around him forever.
All you can control is you and how much interaction you even choose to have with him IF any at all. Sometimes we have to not see toxic people, even if they are family whom we love.
Take care of yourself. Others have to take care of themselves if they even care to. But, that is none of your concern. Focus on you.