Brake controller would deffinately help as far as towing a load of that size. Is the tranny slipping, and losing power like you said? I would suggest doing a nice CAI and a tune on it. I should have a time line here shortly on our dyno tuning, as we can set a load on it and possibly see what might be causing your problem. If she's not squating to hard, I wouldn't do an air bag set up yet, unless it squats real bad. My mom and step-dad tow with an 07 Jeep Grand Cherokee a 71 Mustang and trailor on many occasions with no issues what so ever. Throwing a little more power wouldn't hurt what so ever, and making sure it's in tow/haul mode too. (if you've got it) I doubt you need any load leveling to be honest, because you're right around the limit if I'm not mistaken, but I can double tap that for you. If you can, just gimme a shout later, and I can give you our take on it