The toyota Cmry engine won't stop unless battery is disconnected.

If your engine still runs when you removes the spark plug wires... you have other problems... PLEASE take this to a professional and DO NOT run it unless mandatory.

It's either faulty ignition lock or the switch at the bottom of the gear stick which I've had twice before

The alarm system somehow got activated , this is usually because the battery becomes discharged or disconnected try doing this:
Remove the key from the ignition
disconnect the negative battery terminal
put the key back in and turn to ON
exit the truck and leave door open
reconnect the battery terminal
get in and leave door open, if the alarm horn stays off it should start.

You may need to reset the system.

SEQUENCE ACTIVATED BY THE PARKING BRAKE .
1. While engine is running (key in ignition switch), apply the brakes and hold the pedal down.
2. Move gearshift lever to neutral.
3. Apply the parking brake Once Twice
Note: The system can be set - at time of installation - to require that the parking brake be applied once or twice.
If set for two actuations, pause one second between the two.
4. Remove key from ignition (the system keeps the engine running).
5. Exit the vehicle.
6. Within 60 seconds, close all doors.
7. The system will stop the engine and blink the parking brakes once to confirm the sequence is valid (vehicle is
ready for a remote start command).
SEQUENCE ACTIVATED BY THE REMOTE CONTROL
1. While engine is running (key in ignition switch), apply the brakes and hold the pedal down.
2. Move gearshift lever to neutral.
3. Apply parking brake.
4. Send the start command (Model 801 & 2101 - Model 903 ).
5. Remove key from ignition (the system keeps the engine running).
6. Exit the vehicle.
7. Using the remote, send the STOP command. The system will stop the engine and parking lights will blink once
to confirm that the sequence is valid (vehicle is ready for a remote start command).
http://www.astrostart.com/Support/Guides.aspx

It sounds like you have a bad actuator. This is attached to the starter and has a solonoid that pushes the starter motor gears into the engine gear. If the solonoid is faulty this may happen. Also check alignment of the same.

Sounds like you have a short in the electrical system.
Could be a bad ignition switch. You need someone to check for continuity. etc.

DONT REMOVE POSITIVE BATTERY CABLE FIRST YOU WILL SHORT OUT THE PCM AND THE ALTERNATOR.IN CASE YOU CANT TURN OFF CAR ONE TIME DEAL DISCONNECT NEGATIVE BATTERY FIRST. BUT FIRST TURN OFF RADIO BEFORE REMOVING BATTERY CABLE.YOU NEED TO FIX IGNITION SWITCH LOCK CYLINDER DONT KEEP DISCONNECTING BATTERY WHILE ENGINE RUNNING BECAUSE YOU WILL DAMAGE PCM.AND SHORT OUT ALTERNATOR VOLTAGE REGULATOR.

Sounds like you have a bad ignition switch. Not the key, but the electrical switch.

definately ignition switch gone bad, replace them. go from there.

it sounds like either your having a short at the starter or the ignition switch is bad, I am leaning towards the issue being the starter, usually when the ignition switch is going bad there will be no click,