B: We are human; it is impossible for us not to sin, though we certainly do try. We are saved, by Christ, and are covered with his grace. He forgives me for my failings before I even ask for forgiveness.
C: No. Atheism is the rejection of God; the refusal to admit that there is a higher power. To reject God you need to have heard of him to begin with. There is sufficient proof of God everywhere you turn.
D: There are no 'poor atheists' along the lines you're thinking of. Admittedly, there are probably some who only adhere because of the poor reflection of Christ they see in any Christians they meet, but overall atheists are knowingly rejecting God.
E: There's nothing in the Bible that says I cannot have fun.
