Sooner or later you’ll either have to take action or step away. (or the 1st followed by 2nd) I doubt you can fund him all your life.
IMO better off doing either sooner and while the evidence of what his life looks like without intervention is plain to see.
If you’re his income source, then my advice is somehow you need to use issues to convince him that A) you can no longer afford or will no longer afford to be this, and therefore
you are turning to the state for help with your financial load, (him!)
so B) you understand how hard and miserable the system is to negotiate and try and get him to give written permission to be his DWP appointee and do it for him.
He will probably consider the benefits system beneath him, demeaning, whatever. Your aim is simply to get him in it at any level.
It's likely to incur massive rows, possible self harm, etc, but you can’t carry on like this forever.
You then go into battle with them to get him ESA and or PIP as his appointee, (allows you to explain his condition, obsession, anger etc) long term end aim being to try to get him into a permitted work (self-employed if pretty unemployable) and try to work his way of it.
Even failed attempts will create records onto the system, eventually becoming evidence of his difficulties in themselves, and when everything crashes there will be at least some evidence to work with.
Selling the house won't last him long will it? It's his only asset. Only other thing I can think of is equity release on the house, but that brings it’s own dangers.
. I’m sorry if this sounds harsh, but if you don’t find a way out you can live with, the rate you’re going you’re headed for drifting into being his hidden carer unplanned, with him calling all the shots, and you losing your quality of life.
What happens if you become ill, old, or disabled? It's what's happened here.