Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Now if you think that Harley's quality of life is gone, that does make me very concerned for him. While he could benefit from steroids (if the curling is related to arthritis
or spinal degeneration) and there may be possible treatment for the urinary issue (if it is kidney based or related to a weakened urinary sphincter); we have to ask ourselves if he is enjoying life at this point. This is because if he cannot do at least do those things that have made his doggie life worth living, then we do need to think about letting him go. And based on what you have noted, I am concerned that he may be caught in a body that won't let him enjoy his life as he once did.
So, if he is managing with these old age
issues and still enjoying life, then he may not be ready to leave you (and perhaps it would be worth seeing his vet so they can treat those conditions). Still if he cannot enjoy his life or if his ability to do so starts to wane, then we do need to consider letting him go.
Please take care,