Yo SOG - don't ya think 1/2" is kind of big for a fungus gnat? The descriptoin you posted says they get up to 1/4". Most I have seen are more like an 1/16 - 1/8" in size (and I have one coco grow with more than it's fair share of gnats) Again - I could be wrong - and seeing how you are you - it is likely I am wrong! ...but compare the pic you posted here with the bug in question... doesn't it look like the abdomen is more like an ant than that of the fungus gnat?
If it is a fungus gnat - Azatrol - is THE best product - INMHO. It works, it's organic, and can be used during flowering (root zone application). The downside - it's expensive. Get some sticky yellow traps and set them at the base of your plants. Gnatrol is another good product which I have also had success with... but the Azatrol is amazing - it will actually REMOVE gnats... while Gnatrol seems to keep em in check at best. Again - my humble opinions!
SOG - you are the man - your scene is looking so good!