As Conservator of an aunt and uncle, both afflicted--one mentally, the other post-op from broken hip/fall--I got some pre-need experience of how it is, that
Nobody (not even the dramatis personae!) can rely upon any handy generalizations 'that always apply'. So much is tied up in the unmeasurables
--trust levels, self-knowledge of each participant--there just aren't any must-Do's.

Whatever his awareness of his medical state might be--now and next--or how possessed of self-knowledge generally, I'd think from that (my) experience, that the best case
for all concerned, is just about what you (all) seem to have: few preconceptions and especially, no 'dogma'.
At least, thats the enviro I'd hope to have around, were I Losing-it (mentally, physically or both.) You don't need any advice: You're fine; How am I?
..said one, as two shrinks passed on the street.

(I'd think though, that the optimal situation would be, that all parties are possessed of some sort of.. ~sense of Cosmic Humor?)
Humor seems to bring welcome perspective, even near an Ending--but maybe that's just me. So ignore this.

Luck!