This is the first Doomsday Preppers episode that I've ever seen. Not bad!
Here's my philosophy. I wouldn't spend money, or time, to prep for the apocalypse. However, I wouldn't make fun of full-time doomsday preppers either. This is just in case I will end up needing their help. Remember the story of Noah's Ark? Everyone made fun of him and his family as they were building the Ark. Then when the flood did come, every one of them begged Noah to let them in.
I loved how "the king's" family worked together, and how the king did drills. My only feedback for his fortress is to create a moat around it, which is exactly what a medieval castle has. If there's no moat, anyone with a tank that is EMP-resistant, a canon, or a bazooka can blast any of the castle's walls; and the intruders can march right in. But if you have a moat, especially a really wide and deep one, no matter what weapon you use to destroy a wall, you still have to figure out how to cross that moat!