1) Ok, that makes sense (see #2 below).

2) No it won't, there is no "end cap" effect. The assumption (as previously stated) is that pressure causes no displacements (or loads) on the piping system. Pressure is only used in the stress equations - i.e. the PD/4t term. This is why "W+P1" yields the same element forces as "W".

However, you can turn on the Bourdon Pressure option to account for the pressure strain in the pipe. You can find this option on the "Special Execution Options" dialog.

3) Yes:

LC1 = W + P1 + T1
LC2 = D1 + WAV1