I have a similar setup though I dont use theater tek. I have a 19"LCD Touchscreen as my remote, monitor 2 is my flat panel tv. Different resoultions and everything. Xlobby runs on my monitor, movies, tv and visualizations run on my tv. With Winamp or Zoomplayer.
theatertek launches and causes the taskbar to become visible
.... just a thought, you could launch theatertek upon startup of XL so its not getting launched revealing the taskbar.
You could also drag your movie, audio player to the 2nd screen and let them startup there, then you wont see them until you turn on your projector. Which would be post event play.
You could use xmovewindow plugin to put your movie within a screen so focus wouldnt be lost.
My media launches fullscreen in 2nd window and I never see the taskbar. Hope you figure it out.