I agree that you are good enough to apply for NIW.
We are in the same area. I did that by myself and got approved in a month. I have 5 refrees, 1 from Japan, two from current supervisors, 2 from friends (young Chiness professor in USA).
I felt that the important things is how to organize/emphesis your qualifications in 1) national interest importance 2)how good you are 3) how important are you in the current project in cover letters.
By the way, I was a postdoc when I apply for I140. So I have no doubt about your success as long as you did a good job in organizing your materials. In another word, your hardware is good enough!