MT, I think you are simplifying the problems if abortion in your summary and agrument above.
The viability question is an important point. I agree the child for quite some time after birth is totally dependent on the parent(s) (For some kids that phase goes on for upwards of 20 years!) I think the question of viability is focused more on defining the moment when it is too late to consider abortion a "killing". There is a point at which the fetus becomes something independent of the mother's body. At that point we have to consider the fetus to have the potential to be a live human being. At that point an abortion becomes a "killing" and not just an operation to remove a cellular growth. Please note I am not getting into reasons for the abortion. I am just discussing the actual operation itself and the time limits that I believe should be imposed.
This bears on the "...nobody's business what I do with my body..." argument. If the embryo is just a bunch of cells that is part of the mother's body then she is right to say this. If, on the other hand, that bunch of cells can persist outside of the mother's body then it can no longer be considered part and parcel of her body. The fetus is now more in the nature of a parasite (meant in the nicest possible way, of course) on the mother's body. So I would have to say the mother has the right to say it's nobody's business what she does with her body up until that point.
I don't believe you understood my use of the "people from crummy homes grow up crummy" argument. I did not intend for it to be a reason for abortion. It is a reason not to ban abortions until we can get a better system of birth control out there for the kids who keep getting pregnant. For some it is the only way out of an impossible situation. It is a choice of ruining two lives or only one. Actually it is no choice at all. Life sucks sometimes but we cannot avoid it.
By extension, we need to get some education for the parents so they will understand that little Janie and little Johnny are going to "do it" no matter how much they want to believe in the chastity of their children. And we need to educate those children so that they know what will happen if they screw around and what they can do to prevent it. Unfortunately too many parents think it is their duty to do that and they fail to follow through.
And, finally, we have to get it through our heads that women have rights too. We need ALL men to understand that their sexual needs are not more important than those rights. Until that day dawns this problem will persist.