How do we convince my father-in-law that he can no longer live at home safely?

My husband has been living with my FIL for the last 20 yrs after my husbands mother passed away. I moved in 5 yrs ago and we were married 3 yrs ago. My FILs health has steadily gone downhill. He is an 85 yr old, retired Marine and alcoholic. The family (one brother who lives 10 miles away, one sister in Texas and one in Wisconsin) all feel that he has the right to drink, he has done it all his life. Their mother died from serosis of the liver. None of the siblings do anything to help their father or us to take care of him. My husband is the "baby" at 45 and was never married before me. The siblings all have grown children and are now enjoying their empty nests.
So my FIL won't eat unless I put it in front of him. He wont take his meds unless I put them in front of them and then he usually forgets a couple of them. He sits outside and reads the paper and/or sits in his recliner and controls the TV. He has no friends, doesn't want to go anywhere and constantly asks where we are going, with whom and when will we be back like we are children. He no longer drives. I take him to all his doctors appts, the bank, the store, etc. I have to write out his checks to have him sign or his bills would not get paid. Many of them I have already set up on autopay.
We placed him in a senior community for a 3 week respite stay while we took two long weekends away. He thrived. He limited himself to two drinks a day, he gained 15 lbs and he participated in Bingo and other activities and even went out on the bus for shopping and lunch. When we brought him home, he went right back into the bottle and drank 1/2 of one the first night. He was back to falling down, forgetting, not showering, having huge incontinence issues, sleeping until 2 or 3 p.m. and not participating in anything. He told the caregivers at the community that he did not want to live there because he had a pool and a patio at home although he hasnt been in the pool for years. The community also has a lovely patio. We tried to explain to him the health benefits of living at the community permanently but he said he was not ready.
We have recently returned him to the senior community under the premise that we will be travelling over the next six months. Part of that is true as we have several vacations planned and many long weekend trips to our trailer at the river. Both his primary doctor and his neurologist have stated in writing that he cannot live alone. We have shared this with him.
The Director at the community has said simply not to invite my FIL back home but just keep telling him we are going to be gone again. He has some early dementia and gets confused but he is still somewhat okay if he is sober. After 32 years in the Marines he is quite stubborn and perhaps afraid to give up control? We had lunch with him yesterday and already there is a huge noticeable difference in his appearance and he is back into the activities. He seemed very happy although when I had a conversation later with my sister-in-law in Texas she said that she spoke with him and he wondered outloud how long he was going to be there this time. I told her it was a shame that he sabotages himself when he is at home and that his health and really his life are at risk.
I asked my husband to talk with his sister and bring up the subject of placing him permanently at the senior community, it is time. My husband is feeling guilty because his dad says he wants to come home, of course. Although my husband sees the health benefits of keeping him there, he is afraid his dad will hate him for making this decision. My husband thinks his dad should be able to make that decision for himself. We both saw how quickly he fell apart when we brought him home last time. I asked if thats what he really wants for his dad and he said he didn't care, he was calloused by his actions anymore. I don't want to watch him die in the house, but would rather he live longer and healthier at the community. My husband does have Power of Health Decisions. His sister in TX has Power of Attorney.
How do we convince my father-in-law that it's time for him to live at the Senior Community permanently or do we simply not invite him home again?