I think your first comment here though is really the reason for the historic differernces in how abortion and contraception were understood. The principles were fairly clear, being:
Sex outside the controlling purpose of reproduction is off limits, in much the same way eating without the controlling purpose of nutrition is. (So, to eat or have sex for fun is fine, but if you do that outside the bounds of the biological end of the activity you are a kind of glutton and the activity will likely have negative results.) From this perspective contraception or masturbation are problematic in the same way that using diet pills to allow you to over-eat would be. Spiritually it would be seen as unhealthy, and represent a loss of important self-disapline, but are also likely to result in poor health and social outcomes.
For theologians who thought sperm were essentially tiny people, they also saw contraception and masturbation the same as abortion. That's a scientific error though, not a theological one.
Abortion was simply disallowed because it was seen as killing a person, which is to say, a separate human being. They question of when there was a separate person was quite mysterious however, again, a scientific question. Quickening was a common belief for I think obvious reasons. Today it's conception because that is when, scientifically, you have a human being.
The theological side which says that any human being is a person is a pretty well established Christian principle which gives rise to Christian views on slavery, abortion, treatment of infants and children, the ill, the deformed or medically fragile, and euthanasia, among other things.
It's not the only defensible principle, but I think it's actually a lot more difficult to put limits around it in one area, without compromising another, than a lot of people think. i.e, if a fetus which is a human being but not a person, what other kinds of human beings might not be persons?