The first thing that might help is to sit down and determine (you may be able to do this just because you know him so well, not necessarily ask him a list of questions) what he is getting the most enjoyment from, and the biggest 'sense of himself' from.
Then what he enjoys least, and lastly what is the hardest for him to do.
It's difficult when the things he enjoys most are the hardest but I'm thinking this way - If you can prioritise what he enjoys most, and find ways to help him with what is hardest, and relieve him of what he doesn't enjoy - then he will have the bulk of his energy to put into what he enjoys.
This is different for everyone - my Chris most loved cooking and his tractor when at home.
For example with the cooking, at first he used aides, and some of these aides he made (the kitchen looked like a hardware store!). Then I started helping with the prep - getting things out of the cupboards and opening packaging etc We bought a food processor and that helped a lot too. The things we did kept him cooking to some degree for much longer. Of course he hated the clean up so was very happy to give that to me to do right from the start :lol:
When he allowed me to dress him of a morning it was astounding to find out that it took at least half of his days allotment of energy just to dress and I could save that for him. I guess on that list you can also be thinking what is a pride thing - it was really hard for Chris to allow this the first time. Once he did, he was so astounded that I could dress him within a minute or two when it had stretched to taking him 20 minutes.
Lastly, you have to be able to keep changing this as progression happens and find a way to help him cope with the losses (as you try to cope with them, it's not easy to watch nor your own losses as you can't do things you loved together).
It's kind of quite a personal thing, as some PALS are happy to stop doing something early that is really important to another. Chris's last trip around on the tractor took 2 men to lift him on and then off it. He just drove up, down and all around and the slashing pattern was quite bizarre! (slashing is the big blade you pull behind an aussie tractor to cut the grass as you go)