My diatribe

This is my diatribe/rant to a religious friend.
In a discussion that we had about religion.

But I thought God was supposed to be 100% good, so how did the devil come from God without any other influences? E.g. you can’t get water from pure O2 you have to add some alternative elements into the mix like hydrogen.
Well then why didn’t god destroy him, the devil, as if he created it that gives god the right/obligation to destroy him doesn’t it? Which is what he would do if God was such a perfectionist, as the church preaches.
But that is budiest teachings, to it I believe parts of it but not other parts, but who said one thing that I can’t do one thing that me and others think is good and some others think its evil so what is the cut off point e.g. me and 29 others do one thing that the other 30 think is evil what is it, a good idea or an evil idea?