I'm so happy to hear that MobileSheets has been working well for you so far. As far connecting to Gig Performer, to start, I just want to verify one thing - did you go to Settings->MIDI Settings->Configure MIDI Connections, and connect to the input and output ports for Gig performer? If they are both running on the same machine, you may have to use something like loopMIDI to forward commands between the two. If you've done this already, then I can list out all the steps for sending commands between the two. If you did not actually establish the connection between the two, that would be why you've been unable to send the messages.
Mike
Mike