Can you get someone else to drive and you ride shotgun with the dog on your lap to comfort him? It may get him used to relaxing in the van again.
Or you sit in there with him and get someone else to to chuck a couple of buckets of water at the windscreen.. Sounds mad but maybe it would replicate the bow wave closely enough to convince him it couldn’t hurt him and everything’s ok?
I’m no expert in this sort of thing but I found with my GSD puppy I could get him to cope with stuff that initially scared him by demonstrating that it wasn’t going to hurt me. Like shaking hands with people he was sketchy about or sitting on the air compressor after it fired up automatically and made him wee a little..