1. God made Judaism, but meant for the Jews to convert to Christianity after that religion was formed. Islam is a born of Satan and meant to convert would-be Christians to a religion that kills them.
2. Are you God? No. Then how can you understand him? The Bible says all sins are equal in the eyes of God and he is willing to forgive all sins if you accept Christ as your Savior.
3. Only if you're imperfect to start with.
4. You fear Hell.
5. Jesus Christ did exist. That is historical fact, and as C.S. Lewis said-(paraphrasing here) he was either a liar, a lunatic, or the Lord.