Thanks for the explanation Chilli Monster, I didn't expect anyone to say that there was a common path for fuel to engines.
So, engines apparently very short of thrust and vibrating (possible misdiagnosis of the latter), but whatever caused that seems to require both engines to be in a similar situation as the s/e performance is described as adequate.
Fuel starvation, again? They clearly had more than enough on board as evinced by the post crash fire. And only 700ft to play with.
What sort of glide angle could you achieve at 10k pounds weight?