1 It sounds like, in the twisties, he gets about 1 good second of throttle stabbing in before he has to let up before the corner. Now he's obviously not running qualifying laps, but that doesn't look like it will be very fun.

2 Why do they have the walls so close to the track?  I can understand doing that for the pit straight, but here they have walls right next to the track for what looks like half the circuit; the track looks more like a street circuit than a dedicated race track.  I hope the walls have some give to them, like the safety walls in NASCAR, and aren't just concrete.  Also note there's no place for a car to pull over in the walled-in areas if it has a mechanical failure; they'll need more cranes than Monaco to get busted cars off the track quickly.

What happens if the track isn't ready for the race?  Has the FIA ever canceled an F1 race due to an unsafe circuit?  This could be a bigger mess than Donington Park, since the race is coming up so soon and AFAIK there's no other suitable track available in Korea, even if they could change venues in short notice.  At least when the Donington Park organizers dropped the ball, they could move the British GP back to Silverstone.

3 Peter TnsG, a lot of the walls are there specifically to keep out-of-control cars from leaving the course, then returning in a dangerous way.  Imagine someone blowing Turn 5, skittering across the grass dirt, then sliding back on track near the exit of Turn 6.

Most of the walls seem to be Armco barriers or something similar.  They most assuredly have give, though not enough to allow a car to get through them.  The concrete walls are mostly on straights where there is going to be seating or facilities (for example, the second pitlane on the run from Turn 3 to Turn 4; that's becoming more and more common, to accommodate 'support series' races, like GP2, without encroaching on the F1 pits).  If you look carefully, each of the concrete sections have openings every so often that'll be faired over.  That will allow broken cars to be pushed off the track.  While I didn't notice similar gaps in the Armco, I'm sure there'll be something.

None of the walls in F1 are S.A.F.E.R. barriers, though.  Europe and F1 tend to use "compression barriers", aka "tire walls", to serve the same purpose.

SAFER barriers are a uniquely American design, used here primarily because of the higher speeds associated with oval racing.  Watkins Glen is the only road course in the world with SAFER barriers, and that only because NASCAR runs there, now a requirement for the marque.  F1-style road courses just don't see the sort of speeds that a SAFER barrier would substantially help with.  They wouldn't hurt to have, and it won't surprise me if the new track in Austin has them, but tire walls do the same thing at lower speeds, and cost a helluva lot less.

As far as Korea goes, the track itself is done.  All they'll need to do is put down the curbs and finish the pitlane and they can race there.  Of course, there's practically no seating, and the parking lots and access roads and extra buildings aren't anywhere near being done, and I'd bet whatever permanent cabling is needed for a F1 broadcast isn't in place either.  In effect, they can run the race, but nobody can see it.

If that's the case come race weekend, I don't know what they'll do.  If it gets canceled, there's nothing to be done, no other place to run it.  Oh, they could go to the Mt Fuji circuit instead, I suppose, assuming it's not booked already, but that throws in massive headaches of its own, not the least of which is "what do you do with the tickets sold?"