Yes, according to tradition.
No, Jethro wasn't a Hebrew or a Jew. He was a Midianite.
According to Jewish law, a Kohen can't marry a convert to Judaism.
He didn't.
Nothing. Jews do not seek converts. If a person wishes to convert to Judaism, they are permitted to do so, but Judaism teaches that Judaism should not be proselytized.
No, Obama is a Christian.
yes
Only Judaism
A new Jew.
His father is a convert to Judaism and his mother is Jewish.
Jethro Lazenby goes by Jethro Cave.
Jethro Cave's birth name is Jethro Leroy Ingmar Lazenby.
Lots of reasons. One is that Judaism doesn't believe in encouraging people to convert. If someone wants to convert to Judaism, they're welcome to (although discouraged at first), but Judaism has no mass programs to get people to convert. Nor did it usually have forced conversions like the other religions did. Another reason is that Jews have been heavily persecuted over the years and many were killed.