As I said, I called the manufacturer of the SNAP tests and they recommended retesting again at or after 6 months of age.

Vaccinating is up to you and your vet. I personally have never seen a vaccine site sarcoma in any pet in all my years of being a tech. Felines are still at a higher risk, no argument; however, vaccines nowadays are being formulated to be much much safer and with a much much MUCH lower rate of sarcomas. For example, it is no longer recommended to use the 3y rabies vaccine in felines but the 1y nonadjuvanted one manufactured by Merial.