Matt,

Here's my take on the dilemma...when you pulled the wire from relay to horn you were killing power to the horn proper which is AFTER the relay, this stopped the honking but the problem was further upstream in the actual relay or the horn button circuit.

If indeed the battery is dead I would check the horn button circuit to the relay itself..the relay could be defective and shorting to ground but I would guess it's somewhere between horn button and relay and that is where the problem is. Is this circuit fused..it should be, and the fuse should have blown!

I would look for crispy wires exiting the steering column or going through the firewall..any burning smells in the cab?

If the horn relay was clicking like mad it was probably being told to do so by a shorting wire to the horn ring on the steering wheel.

That's my non-professional take on this. Good luck with the hunt.

Stuart