about NIW

I am working as a post-doc in a University, and preparing for NIW petition. Could anyone help me to answer the following question? thanks a lot

In my understanding, I need to submit the following

1. cover letter
1. I-140 form
2. 5-7 recommendation letters
3. Ph.D certificate (obtained in USA)
4. copies of papers
5. certificate of membership of professional associations
6. evidence of salary which I think is higher than my colleagues ($ 41,000 /year), I am not very sure if this is really considered to be high.
7. check

the above documents have to be filed to USCIS

7. ETA-750B form filed to State Employment Service Office.( can it be filed to USCIS too? )

Could someone tell me if I miss anything, and which document is the most important for approval of the case?

Thanks again