Denise
All I can I say is don't focus on how much time your father in law has; focus on loving him and spending as much time with him as possible. My husband was in outpatient hospice and went through the same process your father in law is going through now. It was heartbreaking watching his health decline. Four days before he passed, he totally stopped eating, slept a lot and was non-responsive. When he passed away he was probably 100 lbs. I know exactly how you're feeling.
My thoughts and prayers are with you and your family.
Flo