You sound determined to do this, but you really need to listen to the very good advice that experienced RVers are offering. Your minivan is marginal at best for towing a travel trailer, and here is why: That tow rating of 3500 pounds does not account for two very important factors; the tongue weight of the trailer, and the frontal area of the trailer. Your vehicle would probably easily tow a 3500 pound boat, because a boat offer MUCH less wind resistance, both to headwind and to side winds. Same goes for a popup.
The age of the vehicle also works against you. Towing is hard, and any mechanical weakness--which you may never even know about in normal use--will likely become very apparent with a ton and a half of trailer hanging from the rear bumper.
The folks telling you this is a bad idea are speaking from experience. Most of us have towed with marginal vehicles or overweight, and we know it's no fun, it can break your equipment, and might end up being unsafe. A rig that is loaded to the max might make it down the road under ideal conditions, but throw in hills, curves, high winds, rain, and other traffic, and you will be looking at a very unpleasant experience at the least. Not trying to scare you, but you have to anticipate bad days as well as good.