Bob, now things a more stable and the burden has lifted a little, do you think you might be grieving for the person your father used to be.
If so it would seem natural. The reality of berevement often seem to hit about six months after a loss.
My mothers physical health is so good that I feel I have had a chance to get beyond this and build up some new and good memories, through short social (as opposed to chore-laden) visits. So the odd lucid conversation which gives valuable family insights, her toddler-like enjoyment of sitting watching punch and judy in the sunshine, her interactions with her grandchildren (who she strangely sort of knows but does not know, but whose company she enjoys), her general (groundhog) day-to-day wellbeing.
Can you plan a weekend away at a point when the weather gets better. Predominently family time, eg trip to a castle, nice meal etc, but time for a specific outing for your dad, say to some daytime cathedral music. Then be firm with him. You were just passing and lucky to have had enough time for this one outing. We will probably spend the summer near my mums again. It has been great to rediscover a town in a positive way and twice weekly short outings are more than enough for her. She is deteriorating slowly so this may be the last summer it is possible, a chance to store some good memories before she starts her final and slow decline.
That said after what you have been through, you may want to spend family leisure time well away.