Dear Mr. BA
... by now, you get to be a 747 expert...!
There were 747 "gliders" a few times, I recall the British Airways running into ashes of volcano in Indonesia... Boeing has a procedure for that, since the rotation of the engines (windmill) is important to maintain adequate hydraulic pressure for operation of the flight controls - that is a first concern... Remember, all flight controls are hydraulic in the 747, no cables...
In the scenario you present, you are correct, FL
280 is a typical initial level for a heavy 747, you should remember that a heavy aircraft "glides better" than a light one... kinetic energy - 9,000 meters, yes, likely that if the pilots remember how to glide, they will be able to make it back to departure field.
I flew in the military, and occasionally "play pilot" with executive jets... an instrument that I miss in the 747 is the angle of attack indicator, as the Learjets have... that wonderful (and simple) instrument would show the pilots the best L over D... the airliners fail to have an AofA indicator, regrettable. When I fly the "Fearjet" I dont care about speeds, I fly with AofA indicator, to tell me what speed to use, i.e. for approach "1/3" in the green is Vref.
Crosswinds - I looked how "George" (named "Otto" in Germany
), the autopilot, flies a coupled approach: crab angle until the flare. I personally keep the crab until 35 feet AGL, then reducing the power to full idle (keeping a little extra power on the upwind side) then at 10 feet AGL, I "kick" the rudders to align the aircraft to the centerline during the flare. That flare is a little firm, compared to my normal landings, since I do not wish the aircraft to drift from centerline, and "float" forever. In any case, the 747 "by PFM - pure f***ing magic" always lands rather smooth.
The only practical consideration in crosswind is "banking an aircraft" with the nose high (4 engine jets with wing mounted engines) since that attitude brings the outer engines (1 or 4) closer to the ground. I do not indulge in a "wing low" attitude and keep "nose high"... could spell disaster.