Well, it seems a few things going on here.
1) The ignition switch has a spring in it to return from "Start" to "Run," so if it is hanging up in "Start," the switch is likely bad. It might have been caused by the wrench you use. I would suggest disconnecting the negative battery cable if this happens again.
2) Starters are not built to stay "on" for long periods of time. The starter motor will likely overheat. Besides, I can only assume it is not healthy for they flywheel gears either.
3) The pin connecting the key tumbler to the ignition switch is metal on my car (1987). You might want to check if Autozone sells something like this. If you wind up replacing everything with push buttons you might consider using relays.
Good luck to you, and be sure to respond back to the forum how you fix the issue and how whichever technique works out.
Cheers,
--Mark
http://www.marksatterfield.com