Go back to reply 47 and commence the connection-by-connection testing. You're tracking Red from battery (or solenoid stud in this case) to the key switch. Somewhere along that path, it's dropping out on you.
If you unplug the key switch, does Red have 12v coming from the fuse panel? If so, the problem lies at the key. If not, the problem lies between the plug from the fuse and the solenoid stud.