Hello and welcome to JA!!!

I'm Billy and i will help you with this.

Since you are loosing power on the coil when your key is in ignition position (not crank), then you most probably have a faulty ignition barrel (where you insert key).
But first of all i suggest you check the positive wire getting to the positive connector on coil (this wire would come from ignition switch so check for continuity), and check for blown fuses.
Now if the wire is fine, and you must change ignition switch, i suggest you do the following test:
- get a spare wire, and connect it from B+ (battery positive side) to coil positive side, then crank the engine, it should work fine, in that case we will have confirmed our suspicion that ignition switch or barrel is faulty. Of course having in mind that you already checked the wire getting from coil to ignition switch.

Regards,
Billy