They Quote the Bible!

During a recent discussion, the subject of homosexuality and the homosexual lifestyle was the topic of the day. During this discussion the Bible was quoted as the source that condemned homosexuality and the homosexual lifestyle. I understand that Leviticus 18:22 clearly states it to be an abomination….end of debate. Well, as a blogger with less than 10 followers and who’s blogs rarely produce comments by the readers, I do need some advice regarding some other elements of God’s Laws and more importantly how to follow these laws.
(A) Leviticus 25:44 states that I may possess slaves, both male and female, provided they are purchased from neighboring nations. A friend of mine claims that this applies to Mexicans, but not Canadians.
(B) What if I would like to sell my daughter into slavery, as sanctioned in Exodus 21:7.

(C) I know that I am allowed no contact with a woman while she is in her period of menstrual uncleanliness - Lev.15: 19-24. The problem is how do I tell?
My dilemma is simple, Are these Laws of God or man’s interpretation of these laws? Now if these are God’s laws, who gave man the authority to change or alter these laws to fit the needs of society?