How do I turn security light off?

Pull the shell left and right while trying to turn the key the lock is preventing it from turning

Try wiggling the steering back and forth while turning key.

either your igniter is dying or your fuel pump is dying

Sounds like your coolant level might be low. At highway speed you probably have enough coolant and with the air passing thru the radiator keeps the temp down, but at idle not so much. Or depending whether you have a belt drive or electric fan. Belt driven, could need a new belt.

http://toolsnyou.com/ go to the link get the service and repair manual and solve the problem

You need a better battery. When you hook the amp meter and read 0.3 the ECM needs to sleep

sounds like the starter inhibitor switch(stops you from starting the car unless its fully in park)

You can find a great write-up here: http://newrockies.ca , it was the only thing that saved my Park Avenue.

maybe it is not completely in park ?? Try starting it in neutral.

If the starter is turning the engine, try re-setting the security system (leave key on till light stops blinking.) If the starter does not turn, you may have some success in re-setting system, if not you need to check battery voltage and voltages in starter system till you find the problem...can be something as simple as a bad connection at the battery. If you need help with further testing, just ask.