The most complicated setup I ever ran was 1 trop 1 beam 2 DHC and 3 turrets... for a total of 4 fire keys. Worked fine, but that takes some getting used too. I had my E key to turrets.... space bar to DHC... F key to my Beam... and I used the number 9 for the torp... Nine was a logical place to put my torp on my tray bar and I would hit it with my thumb on my naga. lol
CTRL + Space would probably have worked quite a bit better for your torpedo.