NSC? Which official? I think you need

more INDEPENDENT letters, obviously.

I had similiar RFE. I am preparing 3 more independent letters. I can just find 1 more citation before Priority Date. I can find 10 more citation after Priority Date. Threfore, I mainly use letters to answer RFE, in which I emphasize the time (before PD).

wHAT IS YOUR deadline? If deadline is within one month, you might be approved. just guess