I can't tell you what to do, this is really a hard decision and personal choice as to when to let go.
I CAN tell you what I would do..having had a few seniors (I have a 14 year old deaf aussie right now), There are many changes sometimes overnite, when our dogs get elderly. For ME, I don't mind that my aussie sleeps alot, when she's up, she is still moving on all fours, tho sometimes needs a little help getting up, she is still eating really good, she doesn't have accidents in the house, she's happy, she is just a little spaced out at times..She is still having a good quality of life
I don't want to let her go, and right now, she isn't ready to go. Thank goodness I have taught all my dogs hand signals, comes in really handy right now with her being deaf
They say, 'you' will know when it's time, and I do believe this, with all my past senior dogs, I just "knew"..
It's tough seeing them age, and I make every day count. It doesn't sound like yours is ready yet