Be very careful to be completely accurate when filling out any application. A claim of "I resigned" in the face of the information in your PRIA record could be construed as misrepresentation. Consider attaching a letter to your application explaining the termination and how dedicated to safety you really are.

You may have to set your sights on smaller opportunities where you can develop a clean record over a period of time....flying charters, frieght, aerial photo...etc. A few years there without incident may help repair a reputation and put you in a better position for the regionals.