That's a counterpoise wire. It makes the antenna act like a dipole. I show that on my channel I used the concept to mount the ht antenna off the radio and still match it to the radio. Good video

I like the backpack set up a lot!! BTW, the screws that mount the belt clip are connected to the antenna so you can put a ring connector on it. You can then attach to a bullet or slot connector so that you can connect your various wires without having to unscrew the antenna. Also, I believe you have to be careful with the way you are currently doing it, to make sure the wires don't accidentally touch the positive lead inside the radio. I'm pretty sure that could short it out.

So, the lanyard loop on the right side of the radio is contiguous with the ground!!! Just connect to the lanyard loop with your wire.

you add any thing to your antenna pretty sure it becomes part of your antenna system

If you are going to play with antennas you should connect it to the center conductor of your antenna connector. It has been proven by MANY MANY HAMS that these ground radials effectively does nothing for a HT reception or transmission. But keep trying. Here is a fact the Nagoya antennas that sell for nearly $20 is nothing more than a piece of speedometer cable cut to i think 18½ inches with a connector to fit the baofeng. The reason that I know this is because I had one fall apart on me. The screws on the back of the radio is also grounded same as the outter ring of the antenna connector. Another thing if you experiment holding your radio closer to your face ehile RECEIVING you will find that it can drastically improve your receive sensitivity. 73 ac0y