Save the realm for himself. He does have Stark blood. After Cersei’s public display, King’s hand Ned Stark’s bastard would be a step up for King’s Landing and that lot. Snow will have the loyalty of the wildings and knights watch men will have to be sacrificed to save realm. But seems I remember Danerys walking into throne room and everything had been destroyed so I’m back to thinking how I would write it.
I have always thought that Jon Snow will, at some point, meet Danerys and they will hit it off, marry, conquer and rule together. Thus, also keeping the Targaryen thing of marrying ones relation (if the rumors are true).