Speaking as someone who has done both, I didn't find the train too bad. We had a 4 berth deluxe sleeper cabin and managed to get a good 6 hours sleep. You'll need to take your own food though as the onboard catering is a little limited.
Air China was fine as far as flights go, (we also got the 0730 - had to be out of the hotel at 0615) but the food was pretty awful. PEK airport was excellent, and we flew to SHA rather than PVG - so much closer to the city but the taxi ride for both needed to be factored in.

All in all, the train is pretty good value (probably not the thing to say on a frequent flier forum, I'll get ejected now!), but you have to understand that deluxe is not necessarily as deluxe as the western view. Lack of Mandarin is not always a problem, there's normally someone around who can help and the stations have all the signs in English and Chinese and are pretty easy to get around.^

AS for worry number 4 - not a problem as you are allocated a berth/cabin on your ticket from the outset.