Building A SHTF Computer Using This Pistol Case, Need some Advice

So some time ago, i was at an Academy store and did an impulse purchase. Spent $50 on this durable, watertight pistol case as seen in the accompanied image. For a few weeks, i have just let it sit in my room and thinking about what to do with it. Then i thought "What about a Portable PC?". So i did some measurements, the interior is roughly 12x9x5 inches in Length, Width, and Depth (if you count the lid's interior). At best i have some components, such as a 10 Inch screen from an old netbook, i already have the controller board to make it a regular monitor for a few purposes.

But a few things im not clear on is what components would best fit this case? I know its too small for most motherboards, and im not intending to use a Raspberry Pi or a Linux OS. And i also want to do as little drilling or cutting into the case as possible to retain its moisture resistance.

If i had to list any criteria for such a build, there would be:
Information Storage
Connectivity to Larger Screens (aka stationary "tower")
Wifi Capability
Emergency Power Source

Thats just off the top of my head, tbh. In short, im wanting to make a utilitarian computer that could survive (and possibly thrive) in a disaster situation of non-biblical proportions, all crammed into a case that was meant to hold a handgun. Keep in mind i have little to some electronics experience, but i have built a pc before. So who has any advice or what-have-you to point me in the right direction?

(i hope this evolves into something pretty dang good. i do believe its kind of a challenge to pull something like this off, going with a case roughly half the size of your standard PC tower)

Picture of Building A SHTF Computer Using This Pistol Case, Need some Advice

Might I suggest looking at dev boards like Arduino/Adafruit. They're small, very customizable and cheap if you don't mind a more complex program/design project. Arduino has many sensors, controllers, motors, gadgets and gizmo's you can add to you project. Arduino also has decent support in their forums.