Wiring in a backup alarm ????

[Mtbuicknut]

I'm attempting to wire in a backup alarm. My plan was to use the in box rv receptacle and tap the reverse and ground circuits. 2 problems have arisen. Problem #1 plug is dead for the exception of the constant 12v. This is caused by the towing package not recognizing a trailer, not sure if this the case or not. Correct me if I'm wrong. I have read that  by placing a resistor between the marker and ground terminals will activate towing package. Again correct me if I'm wrong. If this works my backup alarm will work. I will take a rv plug and install the resistor and leave it plugged in inside the box. When I'm towing it will be removed and everything should work as planned.

Problem #2 If the above works then when the pickup is shut down and the lights stay on for the programmed time, so will the alarm. I know I can turn that option off but I'd rather not. I have seen in my searches of a factory jumper wire that connects at the receptacle at the bumper for a backup alarm so there must be some factory or BCM setting that needs to be toggled. 

Sorry for the long post but I think the info may help.

Thanks Rick