If he were mine I'd take him to the slaughter house and bring him home as dog meat to be honest.
Sounds harsh but if you have a place you can trust, a quick end is far more dignified than the meat mart IMO.
Either that or have the vet PTS and ask them to cremate him, It only cost me £20 a few years back (without getting the ashes back, huuuge amount more if you do want em!!) when a favourite ewe injured her spine. She couldn't walk and had had steroid injections so the slaughter house wasn't an option.
sorry you are having to think about this, but well done for doing so