My silly little dog has a problem

[subi-crosser]

Louie has a problem that can't be corrected. A year ago, he had a 'pin' installed in his lower jaw due to a 'degenerative' bone desease. At that time, the vet pulled 5 teeth from the left/lower side of his mouth.
Over the next 6 months, the 'pin' failed and he lost some teeth from the right side.
He does not seem to be in pain, but his lower jaw is about 1/4 inch lower on the left side, he has no lower teeth till he gets back to the molars.
He can eat soft food, is not losing weight.
This dog has a mouth that is just over an inch long, so 1/4" is a LOT of drop!
As the bone degenerates, his lower jaw receeds. It is now about 1/4 inch behind the top.
His 'attitude' is different, but he still 'fetches' his toy.
Am I being 'a bad steward' for not putting him down?
Should I wait till he shows signs that his pain is effecting his 'quality' of life before I make that trip?
I can see a lot of change in his overall appearance. His fur is losing all the 'shine'.
He's still 'happy', but I don't want him to suffer.
He's 9 years old. I brought him home when he was 3 months.
What to do??