1: Marriage is not a "right", it's a benefit society gives to a certain class of people.
2: Society gives the benefits of marriage to heterosexual couples because long experience shows that marriage of heterosexual couples carries a great number of benefits to society (for example: it civilizes men, making them more productive, and less foolhardy (and therefore less destructive)(see lowered car insurance rates for young males who marry)).
3: There is no evidence that homosexual marriage provides similar benefits to society.
4: Following the age old principle that intelligent agreements give benefits to both sides, it is therefore not in society's interest to give homosexual couples benefits that they haven't "earned".
Marriage is a contract. It's a contract between the people getting married. It's also a contract between, that couple. and the State. Valid contracts require that both sides get benefits. What is the benefit to society of giving a marriage contract to homosexual couples?
Until that's answered, there's no rational reason to give homosexual couples such a contract.
The litmus test is simply this: when same sex couples can marry, what do heterosexual couples lose? Really, how is your marriage any less valid?
That's why this is called marriage equality, because everyone wins and nobody loses.
I could easily argue your other points, bit there's really no reason to do so. Besides, it's going to happen anyway.
Just ask my Kimare.