Hold on, you folded it TWICE? A single layer of cereal box is already pretty stiff, but two folds makes it like a little cardboard spring in there. That is wild to me. Honestly the damp basement thing is the real worry with cardboard since it will soak up moisture and go mushy over time, so maybe try a scrap of composite shim or even a piece of plastic from a milk jug next time. Cheerios box holding up to a 200 lb guy for two weeks is impressive though, not gonna lie.

The messy jobs expose the shop's real skill, @nancybailey.

That line about following along like a zombie is what got me. Here's the thing though, most of those copy along courses are meant to do exactly that at the start, and the real learning kicks in when you close the video and try to build the thing from memory. I get the anger about paying 180 bucks for doc reading, that part is fair, but following along isn't the problem by itself, it's that you never take the training wheels off on your own. Try this with any course, free or paid: watch a lesson, then shut the laptop and rebuild it from scratch with no video, and when you get stuck look at the docs yourself. That gap between watching and doing is where the money you spent actually turns into a skill, and no boot camp can do that part for you.