Controversy and Questions

For years now, and into the future, there will be religious controversy about same-sex marriage. Here are my questions:

Heterosexual marriages are declining already. The percent 'never married' as been increasing in the past 23 years according to the Census Bureau; the percent of 'ever divorced' women by 60-69 years of age has been increasing. The percentage of marriages reaching the fifth anniversary has declined below 90%, rebounding slightly in the past 10 years. Marriages have a median duration of 8 years. Clearly people are living longer than 8 years after getting married; half of the time, we just can't live together longer than that. 'Faux condolences' are given to anyone who plans to get married, and it's the butt of many jokes. Why would same-sex marriages hurt marriage as an institution? What would it take for heterosexuals to be serious about marriage and try to make them last longer than 8 years?

Marriage is defined often as 'between one man and one woman'. Yet in Exodus 21, immediately after the giving of the 10 Commandments, there are instructions about altars and the treatment of slaves. Male slaves were free to abandon their wives and children in the seventh year, if they were married while in slavery. God then deals with the taking a second wife, and admonishing any husband who neglects his first wife, a slave wife. If God is concerned with monogamy, why wouldn't He proclaim this immediately rather than deal with slave wives and second wives--even before dealing with personal injury circumstances?

Opponents to same-sex marriage proclaim that marriage should be denied because homosexuals are practicing sin. Many evangelicals claim that no sin is worse than any others. Does that mean we should deny marriage to anyone who practices greed, envy, idolatry (serving mammon, celebrity worship, and other idols), sexual immorality (like desiring visual and textual pornography), hostility, quarreling, outbursts of anger, selfish ambition, dissension, division, drunkenness (Galatians 5) and respectable sins like irritability, impatience, frustration, anxiety, ungodliness, worldliness, an uncontrolled tongue, lack of self-control, self-centeredness, discontentment, unthankfulness (some of Jerry Bridges' list)? Or are some sins worse than others because they're not 'common' or respectable? Or do you have to have so many 'sin points' in combination in order to be denied marriage, like abusing a spouse which is anger and hostility and self-centeredness, etc.?