Okay it looks like it must be fuse 12, a 20A fuse in the under hood box. There are two wires coming off this fuse, one for the Remote Antitheft Personality (RAP) module, and one for the fuel pump relay. There is no way to know for sure yet which of these two branches off fuse 12 is causing the fuse to blow. You are assuming that because the alarm went off, it is the branch to the RAP. That is not necessarily certain yet.
To know for sure which branch is causing the fuse to blow, you could cut each wire and install an inlione fuse on each wire, using a 15 amp fuse (less than the 20A so one of the inline fuses will blow first). When one of the inline fuses blows, it will identify for certain which branch is causing the problem. Usually a blown fuse is due to a wire shorted to ground, this can be cause by a wire rubbing against bare metal so the strands inside the wire touch the metal of the body. Once the bad branch is identified, it can be traced further for possible chafing.
In this diagram, I am showing how the fuses would be placed, somewhere near the fuse box, cut each wire, and install one fuse for each wire:
Disabling the alarm is a little tricky. It also works the remote keyfobs that allow you to unlock the doors. So you probably want to keep that part working. One thing that is known to cause problems with false activation is the ignition tamper switch. This part is mounted on the ignition cylinder and is known to cause false alarms. If the mechanic has a Ford compatible scantool (Ford's NGS tool can do it), he can look up the last 8 alarm events and see what triggered the alarm. If it is the ignition tamper switch, I recommend permanently bypassing the trouble-prone switch. The switch is inline with a 163 ohm resistor, and as long as the module sees that resistance, it is happy. (Your mechanic can verify the resistance and use some resistors from a store like Radio Shack to duplicate the resistance). To install them, he would cut the wire to the ignition tamper switch, somewhere at the base of the steering column would be the easiest. Then the resistors would be connected to the cut end going to the module, and the other end of the resistor would be wired to ground. This way the ignition tamper switch will no longer cause false alarms.
Here is a picture of the circuit:
What I am trying to say is you probably have two separate problems. The likely cause of the false alarm is what I described, but it may not be related to the fuse blowing. The fuse blowing should be treated as a separate issue, and using the inline fuse method will help narrow down the fault. The repair would be to install a new length of wire to replace the shorted portion, or possibly replace a shorted component.