I am only a year or two younger than you and am full of admiration for you and your wife. It must be an enormous strain to do the amount of caring you do for your daughter. It must be a worry as to what will happen long term if you become incapable of carrying on.
It seems to me that the "savings" that you are making to the care of your daughter compared wit full time residential care are enormous , and the SS should recognise that in providing more care. I think it inevitable that as the demands on the overall NHS budget rise there will have to be increases in taxation or NI.
I worked for 10 years in Holland , with a different form of payment, that worked quite well - the more you earned, the more you paid in insurance and up front - up to a limit based on earnings.
I think migrants to the UK should have to pay their own insurance for the first 4 - 5 years , subject, in the case of EU citizens their being given, free, the same level of treatment as in their own country. Non EU ought to have to pay or have insurance until they have paid into the system for a few years.
In many EU countries you have to have insurance as a UK visitor if you wand a reasonable level of care.