My 11 year old dog unable to control his bowels (see inside)

My pekinese named Joey is 11 and he has had problems for his back legs for a while now. The vet told me it was something wrong with a disk in his back. He does not seem to be in any real pain. The vet said we can put him on medication for it, but it will be really hard on his body. So we have been holding off. Anyways, this is something that I need to have a talk with the vet about about on our next appointment.
I have two dogs, one is a year old. Every once in a while she will have an accident in the house. So anytime I would find a mess in the house, I would know it was her because my Joey would never do that. I was just laying in bed with the two dogs and woke up to Joey releasing his bowels on the bed. He was standing on the edge of the bed as if he wanted to jump down to do it, but he cant jump because of his legs.
I am stressed out, because I know he is getting older now and it would get harder for anyone to hold there bowels with age, so I cant give him trouble for this. But I don’t want him to think its okay all of a sudden to go all around the house. I walk him three times a day but will start walking him four.
Another thing, He is starting to lose it. He barks at the ceiling out of nowhere, and is becoming obsessed with smelling things. Also when were outside and he is releasing his bowels he starts running in the middle of it. I worry that these are all big signs that he is on his way out the door.
I was also curious to see at what point would one decide to put their dog down?
I know it sounds selfish, but I don’t think I could make that decision.
Any advice to give me jellies? Im a little down and out.