Just wanted to make a correction in previous post. If one marries a non-Jew, he violates the lav deoraisa of Lo Tischaten Bam. The case where he violates 4 issurei drabbanan is when he is miyached her liznus. So there are 3 levels btzina: One time znus is 1 derabanan. Designating her for znus is 4 derabanans. Marriage is a lav. The Rambam mentions a pasuk in Navi about kares. It seems that is talking about marriage to a non-Jew, but I will check.
I will also check up the teshuvos in Reb Moshe about hand-shaking.