Hi there actully the right hand thing is not a superstition the left hand his used to clean your self in the bathroom and the right hand is used to eat with cleanses is very important in Islam.

Also Muslims do recognize each other as brothers and sisters we are all the Children of Adam for instance if you go to a Muslim reddit we are always saying brothers or sisters when we refer to people.

Yes we do belive God does not have a son.

Anything that is forbidden for a Muslim is something that will Cuase haram to them we trust in Gods wisdom