PF3 doesn't place you at the gate; you set your starting position at the gate in FSX before connecting PF3. PF3 will then detect your position. From one of my recent flights, calling for clearance:
12/1/2018 12:30:25 PM: 660 - Transcript: 'Clearance Southwest 702 at gate Bravo 5 IFR to Kilo Papa Hotel Lima with information November '
However I failed to notice that in your log, KSDF does not have a Ground frequency. (Sorry, my bad.)
Frequencies for WP: 0 KSDF
Mul - 0
Uni - 122.95
Grd - 0
Twr - 124.2
Clr - 126.1
App - 123.67
Dep - 123.67
FSS - 0
so things are a bit different here. Starting at a gate, after tuning Clearance and getting your clearance as before, manually tune Tower
frequency and press ZERO to request taxi instructions to the runway. Hopefully you should be good to go from there. This is unusual because there are Clearance and Tower frequencies but no Ground frequency at KSDF and I should have seen that earlier.