The "brake signal wire" should be pulled from the HMCSL wire at the LCM in the passenger footwell. I dont recall the color.

If you get a aftermarket light control module, you need to get one that is PWM compatible, I used a reese one on mine.

The brake control you are talking about, hopkins impulse is a timed brake controller, meaning when you step on the brake, it activates the trailer brakes for a period of time, I would never use those types of controllers, I have seen too many of them fail or burn up the trailer brakes. It is best to use a proportional control, they are more expensive, but they work better.

I used to do hitch and wiring on vehicles and RV's I have installed hundreds of systems, make sure you put circuit breakers were applicable and use the proper gauged wire.

As far as the hitch itself is concerned, when I was looking for mine about 6-8 years ago, there were only 2 types, the type that installs like the factory hitch at the bumper mounts, and the type that has the bar that runs under the car past the spare tire. I dont like the look of the bar running under the car so I opted for the OEM type. Looking now I cannot seem to find the style I got. One of the things that the factory hitch does, it replaces the bumper mounts with hardend, and Longer ones, which you cannot get with the aftermarket ones. So I fabricated my own, as well as installed steel plates where needed to stiffen up the body. I used the highest grade bolts, and put lock tight on everything. I went this way because as you have found out, finding an OEM hitch has become impossible, and when you do they want a fortune