Popoki Nu --
Since he is still on top of things mentally and he trusts you, I think you could approach this by laying out all of the possible options with him but let him make the decision. I think telling him he needs to go into assisted living is probably not the right approach given what you've written about him. But sitting down with him and discussing the facts of his health and going over possible solutions involves him in the process of deciding what to do rather than imposes a solution on him.
One thought is to try and convince him to let a home visit nurse and/or part time house keeper lend him a hand a few days each week so that you can have a break and he can stay in his own house and have some sense of control and normalcy. Is this an option where you are?
If he agrees to consider this option you might need/want to be there for the first couple of times that someone new comes into the house until he has a chance to build a relationship with them as well.
You are a good friend to give so much of yourself and your time to help out. It is a tough situation and my thoughts are with you and with Ed. Good luck.
-traveller (Carol)
"It never gets easier, you just go faster." -- Greg LeMond