Not sure, but can you get flee treatment from the vet that you can put in with some worming tablets in his food (obviously, you will not get close enough to do Stronghold)? Would be better for you and your cats as well as, of course, him if he can at least be treated for this. You are at least able to touch him but it may take a few weeks patience to get him tame enough to take to the vet to check for microchip, health check and see if neutered (or get neutered). If you can do this for the little guy he could then have a chance to be rehomed. Cats Protection might help with the neutering. In Leicester they cover 100% of the cost.