When is it time for a parent with dementia to be put into a home?

My father is 89, my mother is 87 with dementia. My father has a difficult time getting around without his walker or cane. They live in a 3 story home with their bedrooms on 2nd floor. My father refuses to put my mother in a home because he expects his children to come every night to put my mom to bed and make sure they have a meal on the table. My mom can't dress herself, she is wearing depends that my dad does not change for her until one of us shows up @ dinner time. We then have to make sure she has eaten for the day and taken her pills before we bring her back up to bed @ 6:30 PM. She can't remember how to brush her teeth, she eats very little, and she will remain in bed sometimes until we get there and get her up to come downstairs. They have a dog that is deaf, that defecates and urinates thru out the house so they have us put puppy pads down all thru out the house. My father insists he can take care of her with our commitment every night and if we can't he states that we are selfish and just thinking of ourselves. My sister lives up the street and she is able to get there every night but it is taking a tole on her. There are just 3 of us in town and no other help comes in because my father refuses to pay for it. He can move to a home at this time thru the VA and take my mother with him but doesn't know what to do with the dog. They do not have enough money to put my mom in a home with out my dad having a lien put on his home to pay for my mom if she goes to a home and he stays at home. How to we convince my father that it is time for her to get more help that we can't always provide with out him making us feel like we are just being selfish.