Would you say this is a 'red flag' in a relationship?

A lot depends on how old he is now and how old he was, when he went to jail and acquired the domestic abuse charge. If all this happened years ago and he's kept his nose clean since, then the chances are that he's turned over a new leaf. If it was only a couple of years or so ago, then you need to be very. very careful indeed. If he still takes drugs, you also need to watch your step with him.