I think everyone advising you has been there and experienced care or arguments about care.
If parents don’t have enough funds people even end up topping their parents money out of their own pocket as they don’t want them to go to some dreadful place that is on the social services list and probably cheaper eg costs them £600 per week instead of £800 etc.
Even if you get funded care at home it’s pitiful outside a care home.
In regards to my mother, my dad paid for her care home - it was £750 per week 14 years ago. My dad had funded care as he had cancer but it was pitiful of fleeting visits lasting about 15 minutes providing his breakfast at 6 am when he was asleep or lunch at 11am. We all cared for him and paid his cleaner and her friend to look after him for periods we could not cover. That worked out about £100 per week… that was with CHC funded care in home! Social care will be the same. It’s inadequate.
Even using the money but then repaying it is construed as a gift unless you pay back interest at say currently 4.5% or 5%.
Your dad will need all his money for his care or you have to set it aside. Unless you intend to care for him there will be a period at home when he needs a little bit more support eg to shop, clean, go out to a memory cafe or Alzheimer choir etc.
His best interests are important here.
If your dad had hundreds of thousands in savings and a decent house I would definitely say go ahead but he does not have much money. So if you intend to pursue this you really need to put money mentally aside for him for when the day comes and he needs support to be happy at home.
He can play a part in so many other ways. For me, seeing my dad at my daughter’s drama performance was a gift as he was often in too much pain to attend. Gifts are not just money. He can gift smaller things eg pay for meals out with him, you and your kids to make memories.
if there is a surplus you will get it when he dies. For now, focus on making memories with him.