Scared Horse-won't stop galloping

Yikes. Is your horse with any other horses in that field? I'd suggest putting him on a lounge line and doing what a previous poster suggested. Start from far away and just show the horse that the cows are not a threat. Poor horse is probably exhausted mentally and physically.
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Just tie him up in a safe place for the day. He can only 'run' as far as the short lead-rope lets him and he will give it up. Let him just watch them from a safe spot for as many days as it takes.

We have 2 American Bison. Every new horse that was not raised with them across the fence thinks they are fire-breathing horse-eaters. They grunt like a pig and we have had horses clear fences the first time they saw and heard them. So, we just tie a horse up where it can see them and they have all gotten over it safely.

We do not just let them run wildly. They can literally cripple themselves and hit fences or go over them. They are safer tied.

The wind storm was making matters worse as a horse relies heavily on all his senses and the storm messes up both sound and smell and his eyesight beyond about 20' is like a camera out of focus.

Lots of good ideas and I'm inclined to think that introducing him to the cattle while under your control is the best way to go as long as you don't behave as if they're something scarey by empathising too much - you have to maintain a very negative approach and I know it sounds silly but its possible to reward a horse for being nervous when you give it treats to try to help it not to be nervous so you only reward when it settles down.
If he ties OK you could try that (Cherie) and if he's not the sort to jump over a fence or run through it you could maybe put up some temporary electric fence as far away from the cattle as possible and extend it a bit ever day towards them
We once had two mares on a field to get some extra grazing where the farmer kept pigs, they spent the first day galloping around like your one did, we stabled them overnight and the next day they just stuck to the fence on the far side of the field but day by day crept closer until by the end of a couple of weeks we had 2 pig proof horses
Good luck, hope it all works out OK. If all else fails you could ask your vet for some ACE until the scarey things look more normal to him