Changing your gear ratio will not change your tow rating. Don't listen to that dealer. Power is not the issue here, its trailer length, weight, stability, control, and stopping ability.
When calculating your overall weights, don't forget to add in passenger and cargo weight and in the Jeep. That all counts towards your overall gross weight.
You are already pushing the limit and since a smaller trailer or bigger vehicle are not options, you should probably invest in a weight distributing hitch with sway control. Also remember to load the trailer properly.
Use a scale to make sure the weight is distributed evenly within the trailer!!! This can make all the difference. There are diy scales you can fab up at home to ensure your trailer tongue weight is proper before hooking it up to the Jeep. I can't stress this enough, if you are going to push the limits, load it properly!
I have another small car that I use to tow and I am always waaaaay over the limit with it. I keep a scale in the trader and load carefully. Everything has a specific place and I know the trailer weight at all times +/-75 lbs. Tows like a dream. If I rush it and just throw stuff in, tows like crap.
2008 CRD GC