I'm trying to come up with tech that fizzles magic.  One-shot items that absorb magic then get fried.

I imagine something made of iron or steel would suffice for deflecting faerie magic. A small shield might be enough for a moderate amount of energy.

I'd love it if he went to Balticon, as I happen to be going this year.

If not, Philadelphia would absolutely love him!

How about not giving him a power, but rather a slight resistance to other powers? He's not invulnerable, but he can take more of a beating than normal. If it's from a supernatural force, anyway. Someone can still just punch him in the face and drop him without abnormal strength.

That would explain why he's a normal but still involved with the powerful set, but make him 'weak' enough to still be in danger and interesting.

The easiest solution is getting yourself arrested so you can have a free 'tour' of the building.  But I wouldn't recommend that.

I would say just come up with your own layout but try to make it consistent. Police stations are different everywhere, but from what I can tell most of the building is given up to offices for different departments. If it's a small city, a whole floor might be given to holding cells, but a big city might only have a portion of a floor devoted to that because there are more stations in the city to spread them out.

So basically, I'm saying make it up. That's what I'd do, anyway.