About 20 miles after putting gas in van ran rough sputters, bucks and dies.

could be alot of issues scan live data and misfire data to determine cause

Use some de-natured alcohol to displace water, and it could be different things causing random misfires, but bad gas is a good suspect.

"Dry Gas" doesn't get rid of water in fuel, it simply goes into solution with it and makes it freeze at a lower temperature. The best approach is to forget about just fueling up for the moment and start troubleshooting the misfire like any other event. If the misfire is subsequently proven to be fuel related, then and only then do you get back to the other suspecions. Take note you said that it is raining, this easily could be just a basic ignition system issue and until you test and prove that in or out, anything else is just a guess.