The fuses for the Horn are:

Fuse 4 in the Engine fuse block near the battery, it's a 200 amp and powers most of the car - if it was blown, the car would not run.
Fuse 6 on the Relay control Module (in the big box next to the battery, it's the module farthest from the battery). It only powers the horn itself, if this is blown, you will only loose the horn.

Assuming those are good (and we know the first one is, since the car runs) I'd look at the Horn Relay, it's on the Relay Control board I mentioned. Bad solder joints on that board are VERY common with these cars. Simply pull the module and have someone resolder EVERYTHING on the board! Takes about 10 minutes.

The circuit is simple, when you push the button(s) on the wheel, a contact is made providing a ground to the relay coil The relay activates, and 12 volts is applied to the horns. I do not believe you would have disturbed any of the wiring to the "clockspring" in the wheel when you fixed the key, and no one else has reported this problem that I can remember. You might inspect the wiring to the horns themselves as well.

The horn circuit is shown on page 8w-41-2 of the service manual, (available for download on this site in one of the technical areas - do a search for it, you'll find it).

I have no experience with the A/C. Fuses all good? Do you hear the clutch engage when you press the button? If so, then a recharge is needed, but the charge is not going to hold if the leak is not found and fixed first. Good luck with THAT system!