This is not what "contrary to natural law" means. Homosexuality is a naturally occurring phenomenon; this does not mean that it is in line with natural law. Some people are born with aggressive personalities; it is not then okay for them to assault people. Natural law is derived from an exercise of practical reason, not from some empirical analysis.

Yes, because both of these are contrary to moral precepts. Christianity has never supported slavery (early Israelite society is not Christianity). Furthermore, although historical Christian society was more oppressive towards women than today's society, Christianity has always been on the right side of history with regard to equality of the sexes.

Christian women were respected and given higher status that women in the preceding cultures. All of the greatest female figures of the Middle Ages participated in some form of religious life; this is because it was the Church that offered women the greatest opportunity at this time. Again, I'll highlight that I'm not advocating discrimination against people on the basis of their sexuality. Gay people are full human persons, sharing equally in God's love, and they should be loved equally also. This does not entail acceptance of homosexual acts.

If someone is born with an inclination to sin, we must love them equally, but this does not oblige us to look the other way when they do sin. Rather, they should be loved and helped with care and tenderness to walk a straight path. As I said, family and friends should never shun someone struggling with this sort of thing, because it is the love of family and friends that must sustain them in that struggle.