I was going to suggest a more thorough disassembly of the keyboard. I don't know how the Apple keyboards are constructed, but I remember a long time ago I spilled a very large Coke on one of my Atari 130XE's and had to completely pull the keyboard apart down to the printed circuits to get all the soda out. The keyboards in those models had a sheet of clear plastic with the circuit traces on it sandwiched inside the keyboard with a layer of dimpled plastic on top where the dimples lined up with the keys. I had to get all the soda off the clear plastic sheet to get it working again. I thought the Apple keyboards might be similar.