Spoiler thoughts --
My impression is that the mom died of an illness. She and the little girl looked happy in the photo, so I feel like the father's abuse began after the wife's passing as opposed to him having killed her. Since he looked sad in the photo, I suspect her illness was known at the time and it was already taking its toll on him. The fact that the master bedroom had not been opened recently definitely implies his grief was too strong to enter after his wife's death. (It's also possible the wife left him as as opposed to dying, but I don't feel that's the case.)
I am pretty sure this game has only one ending.