My Dad (85) has chronic diarrhea, does not want to live. How can I handle this situation?

I am his only daughter and will possibly have to decide for him should he not be mentally cognitive or communicating clearly. He has some kind of vascular disease and his left leg is turning discolored and the doctor says he can no longer do more surgery on the weak veins. He can no longer walk or live alone. Now they want to amputate his left leg.This is a devastating situation on top of all of his other health conditions. I feel totally numb and unable to make any decisions myself. In the meantime the nursing home is charging hundreds of dollars for his care, his medicare is used up, and they are telling me his home has to be sold and he needs to be on Medicaid asap. This feels like a horrible nightmare and I feel unable to cope. In the meantime my personal life is completely spiraling out of control. I feel like a 60 year old delinquent, negligent child for not having prepared for this time myself, in spite of him and his fiercely independent, controlling behavior and attitudes. This should not be such a horrific surprise and I feel completely overwhelmed and foolish to not have seen this series of terrible events coming. How to handle this situation without losing my own sanity is all I can deal with at the moment. This is truly daunting.