While I agree 100% with everything else you said, it needs to be pointed out Fuel Levels would indicate it likely touched down extremely close to the last ping. (if it were not already grounded)
The plane being in the air at 8:11 itself is already pushing what they would have been able to do (barring the extremely unlikely landing/refuel option, of course)
Sure, but that is making some assumptions about information we don't really have at this point
AFAIK. For example nothing anywhere I've read (so far) says the plane was flying for the whole time. Once they lost it on radar it could have gone anywhere in range. It could have landed and took off again.
With only one ping an hour and only arcs from one satellite there is a lot we don't know, especially since we have only been shown the arcs from the final ping. Too bad the plane was not in range of another satellite, that would narrow things down in a jiffy!
Now I'm not saying I think the plane landed but it could have based on what little information we have. I'm guessing a plane saves a bit of fuel while sitting on the ground...
Just as landing would save fuel the plane might also have been "hypermiling". Low and slow might not give max range but it might increase flight time?