1. If you're off the grid, where are you going to get power to run this?
2. If there's no power grid or internet, you probably have much bigger problems than "how can I browse an offline copy of Wikipedia." Those problems would probably last longer than you want to schlep around and item like this.
3. I'm not under the impression that Raspberry Pi's are especially durable, though the SD-card storage is probably the weakest link (though both those things probably have benefits of being common things that allow for the scavenging of replacement parts).
4. If you need to protect from an EMP, I don't think "tinfoil lined cardboard box" will be sufficient. I was reading up on that a couple of months ago when the war started, and it sounds like little gaps in the shielding can seriously compromise the effectiveness of the sheilding.
5. Mil-spec connectors look cool, but if you need to use something like this, you'll probably want connectors that are a common as possible. A connector is useless if you don't have anything to plug into it. Some kind of terminal block would probably make more sense. Using a male connector seems like a particularly fatal flaw (if you used female, you'd at least be able to stick wires in the holes in a pinch).
If you want to usefully prepare for any doomsday scenario, you probably need to really carefully think about your actual requirements in that scenario, and then build to those requirements. IMHO, if it's an actual doomsday, it's probably safe to assume technological society will collapse and not recover for generations, and any high technology would in reality be a short-to-medium term consumable that will break without replacement.