From your post, I'm not sure what year, and model your Jeep is, or what engine you have. I'd be interested to see what it is - never heard of a Jeep that can get 30 mpg in "economy mode." In my CJ, I have an AMC 360 V-8, which got about 14-15 mpg before I installed the Holley 4-bbl on it. Haven't checked it since then.

The mods you mentioned won't help your torque for towing. Even if you get an additional 20 hp, it will all be up at the top end of the power band, and that's not where you will be operating for towing. The single best thing you can do to help towing will be to install lower (numerically higher) gears in your differentials. Of course, that won't help your non-towing fuel economy, but it may improve your towing fuel economy, as well as increasing the torque applied to the rear wheels for towing. It willl, however, be somewhat pricy -- at today's prices, figure $450 to $500 per axle. If you do that, it would also be a good time to install and LSDs or lockers you might have been contemplating, as you will save considerably on labor costs.