I know the etymology of the word but it's not meaningful really. The modern version of the word has a slightly different meaning. The term used to describe people who are opposed to religion/god is anti-theist. It's just semantics but you don't technically need to be opposed to religion or god to be an atheist. Depending on how broad or narrow you define it, being unconvinced is good enough.
Again, that's not true. In religious tradition, heaven and hell are dualities that aim to encourage people to do good and to discourage them from doing evil. You don't need heaven and hell in order to express morality, it's the other way around. Heaven and hell exist (in religion) because morality exists. In contrast to religion, secular moral philosophies are more concerned with worldly consequences, thus the mechanisms which encourage people to do good would have a worldly basis. If you take away heaven and hell, it would only render religious morality meaningless because you are trying to earn a spot in heaven.