Talking to someone hiv+ & poss hep. his saliva was landing on my arm and a piece of his potato chip from his mouth landed on my lip. risk of exposure?

Negligible: If the person you were exposed to indeed has hepatitis, this might be slightly more of a risk than the HIV. But non-blood potential sources of exposure (saliva, etc) carry very low risk of infection and you were exposed on intact skin. I wouldn't worry another second about contracting HIV or hepatitis from this encounter. Stay well:)