I feel a little uncomfortable signing an NDA unless the work has been outlined and the work is to begin.
Also I think you're really cutting out a significant portion of the market with LinkedIn requirements. I understand it's probably needed to filter the plebs, but you should probably allow for an alternative sign-up approach (ie combination of phone verification, require business email, etc).
Altogether very cool! I'm trying to get into InfoSec myself. Good to see innovation in the industry!