I did take a break and went shrine-hunting, courtesy of tips from the human sailor, and added two blobs to my life bar which helped a lot with some of the bosses.
Last night I managed to get the third great soul (even though I was playing with my custom difficulty modifiers*), and today I got to the credits, then finished up the various night-time tasks. I quite liked these as a mostly mellow post-game wander around the place, nicely relaxing after the last boss battle.
Anyway, all in all a great game, I really enjoyed it - it had interrupted me playing Metroid Dread, and kept my attention to the end.
* i.e. was drinking wine whilst playing.