Nice. Car is looking pretty cool too, "for a Kia."
An idea for the air dam would be to cut the plan view shape you want out of a 2x6 board,
seal and paint it, then screw the air dam onto the front of it, starting in the middle. You can trim out the back of the wood too, so it's only a couple inches thick, to save weight. This is the technique i used for my F-100 and it worked pretty well. I bolted straight to the frame behind the bumper mounts, but you'd have to find a different attachment point.
Also, try to make the air dam wider next time, so it covers the tires. Using a wood frame would help with that. Hell, it sounds like you might be working around pallets, so if you can score one of those for free and have some paint lying around, you'd have a free air dam!