I do not know about the number of sins! I think people have tried to identify all references of sin from the Bible and come up with the number 667. Probably there are things which would grouped into it. For example, drug addiction is not going to be there in the Bible. Some might argue that it is referred indirectly in some other form.
Yes! You have to keep on reading the Word of God. It is manna for our souls. God has revealed his will through his Word. We have to dwell in it. Rather than "reading" the Bible, try "studying" the bible. That is, taking the Word into heart and exhibiting it in our actions. You can try studying Bible in various ways. Topical studies, chapter-wise studies, using some reading plans. Right now I am doing one year Bible reading plan and meditating on Romans.
Yes, it is true Christianity comes from Judaism. Christ himself was born a Jew.