I know what you are going through, my dog is probably in a very similar condition the moment and it is horrible.
For the last few months we have been saying 'she won't go on much longer' and each time she seems to rally and perk up! I am expecting her not to last until Christmas, but am dreading if she does and then something happens when everything is shut.
Old dog is on heart tablets and Metacam for her joints, she is wobbly and somedays eats very little. However, she is still perky enough to go for a walk and enjoys her sniffs, coming back to sleep. She is deaf and can't see so well, but I just don't think she is ready to 'go' yet. However, I think you will know and like you, I want to have a plan.
The vet told me they can come out, but will be £80 and would probably bring a vet nurse, if I take her there it is £35 to put her to sleep. They can either have her cremated for us, or we can keep the body and bury at home, or take to the crematorium. I took both my other dogs myself and waited while they were cremated, one was PTS over a bank holiday and the vets kept her in their freezer for me, as the Pet Crem. wasn't open. One dog hated the vets, so she sat in the back of the car and I sat with her with the tailgate open and the vet put her to sleep there - she loved being in the car and it was better than stressing her out inside.
I think most vets expect owners to want their ashes back if they can, I have scattered one dog on the beach (her favourite place) and one is still on the dresser in the kitchen, my other half can't bear to scatter him anywhere, he wants to keep him for a bit and that's fine too.
Sorry, I have bumbled on too long, but I just wanted you to know you are not alone and really anything goes....whatever you feel is right for you and your dog and don't worry what anyone else things.
Hugs...