It seems that you are talking about that he has to appear in criminal traffic court for the expired license. This type of infraction is not the type of offense that makes one deportable. It is highly doubtful that immigration will be there and pick him up. This does not mean that he is not deportable for overstaying. That is a separate ground of deport ability. As I said, immigration will most likely not be there and probably knows nothing about it.

Marriage to a U.S. Citizen would be helpful if it is a valid marriage not entered into solely for the purpose of obtaining an immigration benefit. What's more, if he marries now instead of during deportation proceedings (and I am not saying that deportation proceedings will be commencing any time soon), he will have an easier time. If he marries during deportation proceedings, they will be looking at the marriage much more closely.