To answer my own questions:
While Olive snails are predatory they are neat to have "in my opinion." They seek-out the dead stuff almost immediately. They stay under the sand bed and shoot out like a rockets when they sense something either dead or decaying.
They are not mass murderers as some people portray them to be. But they might feed on small clams and other snails when hungry. I found that mine is picky as to what he eats. He happens to only eat dead pre-frozen shrimp (the kind that you eat).
I still do not know how much or how often they need to be fed. So far, I have done every other day and longest 3 days in between feeding only a small pea size piece of shrimp. I'm not sure if he stores them or eats right away. So, I'm taking it slow... So I don't overload my system...
In my opinion I would only keep one per 20 gallons. I found some info at: Olive Snail - Oliva sp. | ThatPetPlace.com
Other comments regarding tips are welcomed
Thank you for your input.