Hi Ray.

For pushback. Yes. Shift + P 1  or Shift + P 2 is the only way (I have never heard of any other way).

If you look at the 757 tutorial by aussie HERE, he describes how to work out the CG.

The descent should start automatically at the T/D. If  it isn't displaying a T/D then you might not have selected a RWY, STAR and TRANS for you destination airport. There could be another fault, just check out our Topic HERE and take not of Paul's (fsxpaul) reply (#6) for the solution.

Mark