Back in 2011 I was working as a contract CFI. People would lease planes to a "flight school" where I provided by own students and set my own hours. I did not pay taxes, and made less than $9,000 therefore I did not file taxes.

-Do I just list CFI/independent contractor on mt resume/apps?
-Do I fill out PRIA paperwork? I'm not even sure where to send it or what address to put on my applications.

- yes
- no

Airlines will most likely want reference(s) for your time as an independent CFI...FBO manager, DPE, students, any credible person who can verify that you were doing what you claim you were doing during that period (vice running loads of coke up from panama in a 310).

It's always a 310...

As a contractor you're self employed as a 1099 so you are required to file your own taxes (just an FYI).

Regarding PRIA, I have had PRIA requests sent to me to fill out about myself in the past as a 1099.