He has to provide Mandatory Disclosure. If he says he hasn't filed, then you have to dig up something showing the opposite. You can subpoena records. You need counsel.
The Form 4506-T has to be signed by the taxpayer or his/her authorized representative. I do not think this will help you.
Typically the best way to get to income (and perhaps ability to pay) is through normal court discovery procedures -- interrogatories, production of documents, perhaps a deposition -- but it depends on the situation.
You need local counsel to be involved and help evaluate your strategy, goals, resources, and history to really get a proper answer.
This answer or response should not be considered legal advice, and does not create an attorney-client relationship. If you have further questions, I would be glad to discuss your situation further. I can be reached at US - (801) 746-6300, or online at -- http://www.lewishansen.com/attorneys/robinson.html
Not very much will happen until you hire an attorney to start the legal discovery process.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.