The Venture isn’t a van. It’s a minivan, and I think you’re already pushing the limit of towing with it. I wouldn’t try to tow more.
Do you have a friend with a full size truck? Tow the car and trailer to the nearest truck stop and weigh them so you know exactly how much they weigh. Then take a close look at your owner’s manual. I’m willing to bet the Venture’s towing capacity is 3,500# or less.