You can sue yourself, without a lawyer. It will take work to figure out what to do. The reference librarians at the local law library may help...

Your complaint may be to the attorney general or the agency that licenses collection agencies in your state.

The key is the proof based on your testimony, the evidence of payment, and a convincing argument.

Look into a motion to set aside the judgment for failure to lawfully serve the lawsuit and that the debt had been settled.

Yes you can attempt to do so. There needs to be a demonstrated reason to convince them such as bankruptcy being possible.

Consult with experienced malpractice attorneys in the state where this occurred.

Yes there are ways to proceed against assets and income in other countries. The process depends on the law of the country where the wages are...

Yes you may have a statute of limitations defense. Note, You must respond in the legal way and on time with, for example a motion or an answer...

Yes you can. The typical garnishment is 25%

Bankruptcy might be the best option if you or your husband have any non exempt income.