Drag rubbing and hard hit rear end

I own a 2015 dodge charger bought with 5000 miles
on it it was a loaner car for the dealership. I don't
Eleven thousand miles roughly  it started to feel like
the rear end was dragging I didn't have the power
that it used to when I first bought it and I would
sometimes and now more than ever feel it rubbing
in my feet and in the petals. Going on the highway
and also now all the time I feel that Rob and it hits
hard when going over any type of bump or different
roads surrface .  A lot of the times also I hear a
humming from the rear end and knock when I'm
idling also coming from the rear it'll knock a few
times and then stop. When I break it vibrates but
not like a warped rotor it's something different .  
These things have only gotten worse and it almost
feels now that the rear wheels are wobbling and it
looks like in the wheel well of the rear driver side the
wheel is rubbing I looked through the rim on the
same side and I see the upper control arm right by
the bushing on top of the control arm looks like
someone has taken a grinder to the top of it there
are gouges in the metal and there are metal flakes .  
The dealership thinks I'm nuts like always I however
think it needs a drivetrain rear differential or
something along those lines I also think that the
dealership I bought it from didn't tell me everything
on the Carfax and that has been wrecked because
the body does not line up on the frame the doors
are slightly off it is not straight streamlined Down.  
After a bunch of bad reviews I wrote and also trying
to contact the owner or operator of a dealership
that has looked at my car four times I have been
unable to reach anyone nor will they return my call
my thinking is there just waiting for my warranty to
run out so I have to pay them to fix it somebody
please help if they understand at all .