Does it measure resistance (Unit is Ohms)?
Your getting confused hear, current and voltage are two different things, but it really doesn't matter in the context of this post.
You say the wires all read 12V. When do they read 12V (I.E. Do you have anything connected to the ignition barrel)?
No. You need to determine what the wires are actually for. When you saw wire the wires to switches, what are you meaning? Your ignition barrel will have a 12V constant feed (battery feed), In the off position, this is not connected to any wires. In the ACC position, the 12V is connected to the Accessories wire. In the On position, Accessories is and an On wire (powers fuel pump, computer, ignition etc) are connected to the constant 12V. In Start position the ACC is disconnected (so the starter gets as much power as possible), the On is still connected and the starter wire is connected.
Stop jumping to conclusions, take your battery cable off, set your multimeter to resistance, attach one end to one wire and then with the other end, determine where this wire is going by probing the end of the loom. Then work out what that pin (on the computer) or component (starter solenoid etc) is.
You are just going to kill something otherwise. Also give the shop a call.