If I may verify the processing times involved in NIW. Since it falls under EB2 category, I am assuming it may be a long time before I can get my EAD card and be able to change employers. Also, I want to confirm if there could be issues if I change employers during the process - If so, I'd prefer to change my current employer before starting with it.
You can change employers any time if you are a self-applicant and will continue to work in your stated area of national interest. But NIW priority date will take the same time as a normal EB-2 application does. See: http://www.immigration.com/visa-bulletin under employment-based category 2.
What does the State Department recommend as the best method for an attorney to bring arguments of admissibility to the Post's attention?
The State Department says that an attorney should present a cover letter that summarizes the issue and a legal memo at the time of interview.