He spent a couple of thousand on vac-pac food which probably won't even be good for all that long? Yeah, he's a bit bonkers - especially if he is convinced he is preparing for imminent war/conflict rather than a possible natural disaster or problems with food distribution.
That said, I don't think there is anything wrong with having some decent stores built up for 'just in case' - but I wouldn't just go and spend that kind of silly money on special stuff. More sensible to just have a good stock of stuff we would normally eat, drink and wipe our bums on 
So DH and I have several crates of bottled water and wine stashed away and I keep a lot of tinned and dried food rotating through my food stores so the oldest are always being eaten first, the amount in there varies, but there is always enough food/water and toilet roll in the cupboards for us (and the cats) to have for a month or two without going shopping... though DH always says he might have to eat the cats and save their food for when he is desperate 
We also have bug out bags (otherwise known as OFRS it seems) packed and ready in the hall closet with change of clothes, med kit, torch, blanket, multi-tool etc packed into it.
But we do live in an area somewhat prone to tornadoes, and there was some pretty bad flooding a couple of years ago too. So that level of prep is just pretty sensible for us. If we lived in London I don't think we'd be quite so hot on it!
So to summarise - Being prepared for 'just in case' is fine. Making paranoid preparations for specific things which probably won't happen isn't so fine.
I think he is one to keep an eye on as it sounds like he may be taking his preparedness a bit too far and any evidence of his inner Rambo/Bear Grylls taking over should be eyed with caution. But then again, having lots of food stashed under his bed may have eased his mind and he will now be able to carry happily on his way without further stressing. In which case - fair enough if he can afford it.
I think asking him to tell you more about what he knows and how he found it out might be a good way of gauging just how obsessed and paranoid he is.