The entirety of Wikipedia is only like 50GB. You can literally carry it with you on a thumb drive.
It’d be hell to actually view since that’s only counting the raw text info, but you could conceivably do it. If you include things like XML and edit history, that climbs to something like 20TB. A lot, but still technically possible. Especially if you compress it (which drops it down to like 200GB) and only decompress it when you need it.
For what it's worth, this metric is based on only the text, itself (no media), and after it's been compressed. Wikipedia actually has an article about this:
It's based on official military survival guides plus other updates and resources. Maybe you could try finding a downloadable Survival Guide PDF that you could hopefully use offline.
I'm not sure, not very familiar with Apple/iPhone ecosystem.
Thank you for sharing this. this looks incredibly useful and although I hope I never have to use it having it installed puts my mind slightly at ease, yknow, just in case.