Since the company is located near me in NYC, I talked to their team about the range concerns, and they told me that they conducted testing in Manhattan and were getting 3.5 miles around Central Park and 1 mile on the ground in Brooklyn. In the open desert in Utah, they were seeing distances of 6+ miles.

As for the gain issue, their CTO said their receivers are up to -126dB sensitivity, but the antenna doesn't have any gain.

(updated)