The only way to reverse the USSC on gay marriage is a Constitutional amendment. Period.
Anything else is a total waste of time and a distraction.
Not really. Marriage is a non-state institution that pre-exists all organized religions (certainly all extant today) and the very notion of a nation-state. The fact that the government has chosen (for good reasons) to regulate it (for instance to suppress incestuous marriages, child marriage and the like), and to support it (since it is a social good) with favorable treatment under the law, does not make it a state institution. If each of the several states chose not to have a corresponding state institution and SCOTUS ruling about marriage law would become moot.