Typically, it takes less energy to tow a given weight than to carry it on the vehicle.  

I'm guessing that that trailer is fairly sturdy and heavy, and loaded with gear; + 3  people and gear in the jeep? and you have a siginificant load to haul - so it takes more gas - putting the same load on the vehicle isn't going to be any better.   Back off the gas pedal a bit, and you may see some improvement, but then, there goes your 8 am start.  Jeeps aren't know for thier exceptionally fine gas mileage - live with it, or buy something else.

I get about 15mpg @60 with my F-150 with a boat on top, especailly if (and that's almost always) I get a lot of headwinds on the trip.  Last weekend was particularly windy going out, and when the wind gusted stong, I instantly lost 5 mph.  My Dakota does better - I can get about 20mpg wtih boats on top, but that's running at 60; go up to 65 or 70 and the mileage goes down by 3.  

It does make a real difference if you can slow down a bit.