Curiousdan
I want to be kind but the truth is I've been getting crabby lately - hence me calling out on this forum for advice.
Things my father won't do: see a GP, join a group or class, have a cleaner, go anywhere with any one for any thing, get the house sorted (crumbling plaster and broken furniture)... maybe he is happy living this way. It's me that has the problem! But I am trying to adjust my thinking.
The dog is the only thing that keeps my father going (even though he doesn't walk him etc). Think the most frustrating part is we've all been there for him since my mother died but he's waved us all away (and sometimes it has felt like a snub).
But you can't help someone who doesn't want help.
Take care of the dog, check in on your dad and so long as dad is eating well and seems OK living the life he's living then leave him be.
FWIW, AgeUK have a social thing where hosts invite a group of older people to their house for meet ups and coffee. I was a host for a while and quite enjoyed it. Guests are picked up/dropped up by volunteer drivers.