One option would be to simply serve the divorce by certified mail, perhaps with restricted delivery so that the current resident can't sign for it if he has moved, and see if he signs for it. Another would be to hire a professional process server.

The best is likely to retain a lawyer to handle the issues of locating the ex-spouse and serving the divorce. It costs more than do-it-yourself, but with a long separation, domestic violence issues, and a possibly unknown address for service, it may save the wife a lot of time and trouble.

A standard protective order does not prevent the wife from contacting the husband -- only he would be restrained -- but I can understand why she might not want to contact him, or may be concerned that he would use any direct contact to argue that she is no longer in fear of him and that the order should be lifted.