This sadly is something we all face and the question is knowing when the time is right, yes I have asked the vet in the past and got the same kind of answer. It truly is a dreadful time and my heart aches for you.
I don't think anyone can tell you what to do, it just seems to slot into place and you seem to know. Seeing your boy cry in pain is so heartbreaking.
Is he still clean inside the house, for me my last dog became so distressed with messing and wetting in the house and seeing him poorly yet so distressed over that this was awful.
I would spend loving quality time your brave boy and take each day as it comes and I am sure you will have clarity soon.
Sending