Yes. There is no point, really, in persisting with nap time. It is too problematic, and your son is too young to participate in the sort of qui-pro-quo you have tried. There are times during our children's growing up years when it is very sensible to, as they say,
cutCuts and puncture wounds our losses, and I think you have reached one of those times. As time goes on, your son will stop these behaviors, but that will come mostly as a result of development. Rather than continue to try to make the nap time successful, you'd do better to eliminate the problem by eliminating the nap.
My son would also smear his BM at that age... but it only lasted for about 8 months. What really seemed to help was making him clean it up himself.
Further, after years of unsuccessful potty training, I'll let you in on the secret that really did the trick - a small toy self above the toilet within direct view while sitting. I would pick up small prizes (bubbles are a favorite!) and he would get a prize for using the potty... or just really trying! That finally worked!