That's a bit to much trailer for your 1/2 ton. You should be looking for a trailer in the 5000 to 6000 gvwr, not 8500, thats for a 3/4 ton truck. 6000 gvwr trailer will have a 700 lb tongue weight, which is as big as you should go. Find a trailer ...
I agree with the earlier comments, check the 7-way plug. If the 7 way has a plastic cover for when not in use, make sure it is not trapping water, that will complete the circuit and your running lights will come on.
A better way to go about your search, since you already have a truck, is to determine what the limitations of your 1/2 ton truck are and then shop for a trailer at you can tow with the truck. Hint, I would guess payload or rear axle are going to be ...
Overall looks pretty good. I cant comment on Heartland or Mallard quality, have never owned one. One thing I would check is what do you have access to when the slide is pulled in, can you get to the bathroom, frig, etc. This is very helpful when o...