I'm probably not a good one to tackle this because I fall under the religious conservative category. I do realize you can't really legislate morality, but at the same time I don't think we need to legislate immorality either.
Out of the three things you mentioned I'm in favor of two of them. I don't know the stats on whether marijuana users tend to move on to other drugs or not. So for the sake of argument let's assume it's not a gateway drug. As for abortion I'm opposed to it but realize it's the legal and no one is going to change that. Even the talk from staunch conservative politicians tends to be more about fund-raising and attracting social conservative votes than actually doing anything. But even though it's legal and will likely stay that way I don't think organizations that provide abortion 'services' need to be funded by the government, i.e taxpayers like you and me.
I also believe marriage is intended to be between a man and woman. No need for gov't to get involved and overturn centuries worth of tradition and change the meaning. If people are homosexual, so be it. If they want to live together so be it. But I don't think they need to have any legal status as married couples or for the definition of marriage to be changed. I also think if anything it should be a state issue not a federal issue. But I'd just be as fine if gov't wasn't involved in marriage on any level, homosexual or heterosexual.