some idea

it sounds like they are asking you to argue the third requirement in NIW. They are fine with the first 2 requirement though.
What fsa2000 said does make sense. You do need to collect objective evidence. Such as official professiona recognition and /or standing on you relating to your employment.Copies of grant application/award documents for all research in which your participating at your university. Also your patent, citation. All of these materials that can identify you as someone beyond others. If you do have any evidence as listed in the notice, go ahead and prepare them.

But the problem is that, you probably have presented these objective evidence in your initial submission. Therefore, in order to answer their request, you have to collect something new. In such a short period, you probably have to get new independent letters.

Therefore, my suggestion is:
1. You still have chance. Don't give up that easily. YOu have gone that far. If you give up, you will have to start over later. And it is painful.
2. Hire a good lawyer. Ask friend for the recommendation. Especially someone went through RFE. You need some professional help. I think that my lawyer is pretty good at RFE. But I don't want to put his name here as ad. If you want, you can send Qiaoqiaohua to me and I will answer.
3. Think about the case yourself. Try to organize your previous materials and some objective evidence that you might be missing last time.
4. Get some strong independent letters (3-4). Ask everyone you know for help. Especially your boss. Get a list of the people who might be willing to help. Ask them one by one. Don't be embarassed. You gotta do what you have to do.
5. Stay calm. You have to go through this process and you are the one who is in charge of that. Take it as life experience. I said that because I have gone through similar, even worse experience.And now I am grateful for what have happened to me.
6. Good luck.
Hope that help.