The ONLY way you can do this is remove the rear driveshaft when you tow. Like JMonroe said, sell the dolly and setup the Jeep for towing 4-down.
Also, check Craigslist for tow bars. I went with a friend of mine this weekend to check on a listing for a Falcon All-Terrain towbar. It was brand new and had never been used. Also, the guy threw in all the mounting hardware and cables for a 98 Jeep Wrangler which my friend happens to own. Got everything for $250.
Mark Anderson - FMCA 351514 - Louisville, KY
2007 Sportscoach Pathfinder 377DS - Freightliner XC
2006 Jeep Commander
Cricket SW3 Personal Transporter