Will there be joy again?

8 months and 2 days ago I was looking to the future with starry eyes and big dreams. I was [finally] engaged, I picked my venue and my dress and I enjoyed fantasizing about living with my husband-to-be. I was looking at honeymoon destinations and thinking about names for our kids. I was over the moon. 24 hours later, the moon fell from the sky, the stars faded, the sun set and the dark clouds rolled in. My fiance's mom died and his whole world collapsed taking all the joy down with it.
The months following was a whirlwind of moving in together, funeral planning, legal paperwork, sister's graduation and the transformation of my fiance from funny, loving man to cold, bitter, detached, abusive stranger. The man I fell in love with died with his mother. The dark spirit left behind has me hanging on the fence between staying and leaving every day. If I stay, how long with I have to endure the mood swings, the lashing out, the anger, the violence. If I leave where does that leave him, abandoned all over again, alone with his pain. How much has my commitment obligated me to take? How long is too long to wait for him to recover? Should I even put a time limit on it? Well unfortunately the biological clock ticks away whether you are in a position to become a family or not. But I can't put my clock on him. 
If I stay, will there ever be joy again? Will we laugh again? Will he look at me the way he did when we fell in love? Will we be able to have a happy marriage. Will we be happy at all? The unknown is so terrifying. 8 months is not nearly enough time to cope but I honestly expected some progress. Maybe my expectations were too high, too unrealistic. I'm so lost.