The vast majority of atheists are atheists because they don't want to be like their parents or the general population.
Honestly that's probably a good source of atheists. When something is pushed on you, you won't like it. They were probably tired of all the weird rules and wanted to know their options.
Deism is the belief in a god that does not intervene with human affairs.
A deistic god could have created the earth and life, and then ceased all interaction with it.
There's a ton of things in the Bible that Christians completely ignore. You can't really say that ignoring one of them makes them not Christian, but ignoring all the other ones is completely fine.
Yes, and by not interfering with humans, a deistic god cannot create a book of rules.
They really shouldn't be ignoring any rule, which includes not eating shellfish, having premarital love, masturbating, or wearing two different types of cloth at once.
There are all different kinds of Christianity, so don't get stuck with one.
I'm assuming the bible is a basis for Christianity, though.