You seem to have a pretty strong case. He has full custody. In most jurisdictions, the ex will need to prove that there is some reason that custody should be changed. The longer he has custody with no child problems, the harder it will be for her to take them away. Her DV will also weigh against her.
Couple of other things you might document. Has she moved around a lot since the split? Has she had multiple BF since? Any arrests? Conversely, how about your son? The court in most cases looks for the parent that offers the most stable environment for the child. He needs to make sure he is the one doing this.
I would just sit tight. You never know what the judge will do, but it looks pretty good from here. You may not need to use any derogatory (sp?) information about her, but it always helps to have it. Just in case. “Pray for peace, but prepare for war”