The argument at 1:00 assumes that children can/should result from all marriages, and that familial roles are rigid/static. It also ignores the very real possibility of adoption by gay couples, as well as children by previous partners, surrogacy, and artificial insemination (Thanks, Cantata).
Arguments from nature (such as the one around 1:20) are logically fallacious.
Your slippery slope argument starting from 1:40 assumes that consent will no longer be required by both parties being married. Such a requirement means that animals, inanimate objects, and cartoon characters cannot marry, as they cannot sign a marriage license.
From 2:45 you're essentially arguing against all marriages that don't produce children, including marriage by the elderly, the sterile, and those who simply don't want children. You also, again, are ignoring adoption.
Around 3:30 you're making a slippery slope argument again, and are ignoring that the "natural meaning" of marriage has changed many times over the years. It's not just a fallacious Appeal to Tradition, but an appeal to a
false tradition.
All in all, I'd say you argued the case against gay marriage about as well as anyone ever has, so props for that. Just need to spend a little more time drawing your conclusions.