Nobody is banned from marriage because of their sexual proclivities. Everybody can marry as long as you marry a member of the opposite sex that meets the age and familial requirements. That is the definition of equal under the law.
Sorry but no. You are missing the point entirely. You are promoting a certain behavior and rewarding those that engage in that behavior with financial goodies. That is a recipe for disaster. This allows the government to social engineer.
The state can offer a marriage contract that allows a man and woman to be married and no legal problem arises from such. It is when you reward that behavior with government goodies is when the problem starts.