1. That is a false claim - Gamenab didn't even cite the correct FPGA model when he made that DRM claim.
2. G-Sync is actually good down to 1 FPS - it adaptively inserts additional redraws in between frames at rates below 30, as to minimize the possibility of judder (incoming frame during an already started panel refresh pass). FreeSync (it its most recently demoed form) reverts back to the VSYNC setting at the low end. Further, you are basing the high end of G-Sync only on the currently released panels. Nothing states the G-Sync FPGA tops out at 144.
3. I use the word 'experience' because it is 'my experience' - I have personally witnessed most currently shipping G-Sync panels as well as the FreeSync demo at this past CES. I have also performed many tests with G-Sync. Source: I have written several articles about this, including the one linked in this post.
5. I believe the reason it is not yet released is because Nvidia wants to be able to correctly cover more of the range (including the low range / what happens when the game engine hitches).