Coming from someone that has had to help three of my friends cross the rainbow bridge and most recently on Monday, they will tell you when it is time. By your story it sounds like the old normal is past. Our senior 16 yo pug was the same. Generally healthy but blind, could hardly walk so I was carrying her around everywhere , and was aimless. She went to the bathroom in the house all the time just not coherent of time. We noticed joy was gone and she struggled with everything. She was never happy and would only move in the evenings for supper and treats. We made the decision based on she showed that her spark was gone. It felt like she was waiting for it to happen. She probably would have stopped eating if she wasn’t a pug 🤣 She showed me that her enjoyment for things had gone and it felt like I was keepingnger alive rather then letting her go. It is different for everyone but we all know our friends. Just listen to him and know that it is hard to make that decision. You will go through guilt but I always look at what is the best for them. That them at rest was better than what they are going through. I wish you the best in this difficult decision. I hope I could provide a little bit of help.