The differences between the P3S and P3A/P are such that while I "want" those extra features, I personally wouldn't get any practical use out of them. They're great birds with great cameras and controllers, but what I have is more than sufficient for my needs. :)
Yes you will want to connect to wifi, enter camera mode on dji go, then browse around the area you will be flying on the dgi go map which will cache the map to the device.
1) The pixelation is just the video downlink from the drone temporarily losing resolution due to signal interference/loss. Nothing to worry about. Happens all the time.
2) You need to sync all the maps to the device by browsing/zooming/etc the map where you'll be flying while your Shield is...
Flimsy is fine as long as it's strong enough to push down grass you're landing in/on. I got one from Polar Pro but it doesn't line up properly with the gimbal regardless of the position I put it in. Truly worthless. :-P
(In other words, point the nose of the controller at the aircraft (for the video signal) and keep the adjustable antenna as perpendicular to the craft as reasonably possible.)
Link stating basically what you said: KEEP CALM: The FAA and sUAVs/Drone Rules (Final UPDATE) by Jeff Foster - ProVideo Coalition
They're safety guidelines, but not enforceable laws.
That said, I plan on sticking to the recommendations. The last thing I want is to be the cause of some incident...
Yeah, that's pretty much the key. You paid for a new unit, got a broken unit, then a provably pre-owned unit. Sounds like their note about updating the firmware, etc, may have been a cover for selling you a pre-owned unit.