Wipers, radio and heater fan stopped working while driving

Hard to say how much water was getting up into engine bay and causing problems. First I would check the battery is secure and cables are tight, not frayed/corroded. Then make sure cover is on under hood fuse/relay box and all fuses/relays are good and well-seated. Don't jump to conclusions on ignition switch. So many electrical issues can be tracked back to the battery.

Since you mentioned the ignition switch, just for your own piece of mind check out whether or not the van had been under the recall years ago. It may help to know that. If it is then I'm guessing they may not do anything because it may be too late to get that serviced, but be sure to only put the key in with nothing else on the key ring.... dang electronic ignitions. Other things can effect that too but I figured I'd mention since I had the same problem and with the recall they fixed mine for free and I've never had issues since.