Cannot get my chaeto to grow for the life of me!

[Millepora_Maniac]

Flow is not an issue, you don't need lots of flow. Just need water to pass through the mass.

I used a compact fluorescent clamp light myself, it worked fine. It looks like you have measurable nitrates and phosphates, so it should be growing.
Maybe try changing the bulb in that clamp light to something more plant spectrum (6500 k) Seems a little overkill to buy an expensive LED system just for chaeto. That little light should work.

Good luck dude!