The real-world error bars are quite wide because of the impact of moral character on a person's value, but sight unseen I would give the last seat in the life boat to the non-mentally-disabled person almost every time, yes.
Am pro-abortion in extreme cases involving rape or abuse
See, now that's a viewpoint I don't understand at all. The question of whether or not killing a fetus is killing a person is not affected by the circumstances of that fetus's creation.
A life isn't really that simple to define but yes. There are many "sins" external to the creation of life that warrant consideration of carrying a pregnancy to term. Some of them include inbreeding. At that point am okay with letting the society or the creators decide on the baby but am a bit more liberal on life created as a result of violence or psychological manipulation.
Am pro-abortion in extreme cases involving rape or abuse
See, now that's a viewpoint I don't understand at all. The question of whether or not killing a fetus is killing a person is not affected by the circumstances of that fetus's creation.