The treats won't hurt him Sandra, they won't be much use either but if it keeps his attention and your hands and pockets clean then carry on

As for the oils try not to use capsules and go for bottled natural stuff that isn't too heavily refined but if you can feed him raw eggs and tinned sardines, mackerel etc he shouldn't need any other supplements. If your really want to give him supplements then why not have a look at the Dorwest Herbs website as they will have a few things on there you could use, failing that Holland & Barret but most of their stuff is refined and more suited for humans.
Sandy