So, I went to the Glow and investigated for a while. I got the power on, got some loot, etc. I leave, and use the Geiger counter to check my rad levels.
6600.
What can I do? I can relieve about 150 of it, but that's it. Once a day goes by I die. Is there anything I can do, or am I screwed?

Outside of going back to an earlier save, no.

Next time, remember to eat your Rad-X before (prefereably click on the map right before you reach the green circle and eat it there) and also have some rad-away and use it when you're inside and take a last one just before you start travelling back.
I used two Rad-X and 3 (maybe 4) Rad-away myself and that was enough for me to not even get nauseous on my way back. (one rad-x before and one inside, about halfway through the level)
One more thing, if you fail with disabling the robots it takes 5 hours gametime whereas a succesful only takes ten minutes, so save before you do it in case you fail. (since it'd ramp up radiation quite a lot)