I'm jewish am I more susceptible to becoming an addict?

Probably less. There are moderately strong cultural barriers to jews becoming addicted. For instance alcoholism is very low among jews. It is not a matter of heredity but of social convention. Some young jews do defy these conventions and addiction is possible.
No. Whether it be ashkenazy or sephardic there is no genetic predisposition towards addiction. There are also no cultural or societal correlations in the literature.