Except the first assumption that e^x = its own integral, everything else actually makes sense (except the DX are in the wrong powers). You simply treat the "1" and "integral dx" as operators, formally functions from R^R into R^R and "(0)" as calculating the value of the operator on a constant-valued function 0.
EDIT: the step 1/(1-integral) = the limit of a certain series is slightly dubious, but I believe it can be formally proven as well.
EDIT 2: I was proven wrong, read the comments
That's the thing about physicists doing math. They know the universe already works. So if they break some math on the way to an explanation, so what? You can fix math. They care about the universe. It's pretty cool sometimes. Like bra-ket notation is really an expression the linear algebra concepts of dual space and adjoints. But to a physicist, it's just how the math should work if it is to do anything useful.
So yeah, this post looks like nonsense. Because it is. But there is a lesson that "math" should work like this, and there is utility in pushing the limits. No pun intended.
Edit: I'm not claiming this is a useful application. It's circular reasoning as this post's parent alludes to.
I don't believe you can just factor our e^x in the second step like that. That seems in incorrect to me. Then again I've been out of calculus for years now.