Why not seek to get an appointment with the judge who ordered the divorce?? Get the ex's rights terminated.
Termination of parental rights will be the only way your husband can legally adopt his step children.
You may have a strong case against the ex if he is failing to pay child support and has skipped the country. And it sounds like he wants to terminate his rights.
There are online legal attorneys who offer free advice.
http://www.nolo.com/ http://freeadvice.com/
There are web sites that offer legal forms for you to go thru this process on your own. The costs are much less than an attorney's costs. There are filing fees and court costs. For instance: filing for divorce costs around $125.00 then court costs.
Good luck
EL