Please, please, please rehome him via a reputable rescue, not via a private rehoming or an advertisement.
Rescues are not judgemental, and will be able to ensure he goes to a thoroughly vetted, homechecked adopter, with lifelong backup in place.
Given his age, try the Oldies Club as a first stop.
You will need to supply all his documentation, including his vaccination records, his chip details and any other paperwork. Make sure he is up to date with flea/worm control, and prepare a little crib sheet giving his daily routine, his habits, any training, diet, any allergies etc.
Given the time of year, be prepared to wait a little while for a rescue space to be available. Unfortunately at this time of year, there is a flurry of hand-ins as parents are unable to cope with kids off and dogs, and also don't want to pay for holiday kennels. Also please be aware that the vast majority of rescues are run by volunteers so dont' expect miracles overnight, and bear in mind that a foster place or adopter may be elsewhere in the country, so it may take a few days to organise transport runs.