Margie,
With all due respect to your research and your opinion, I think we've boiled this down to issues of communication and semantics, not science.

The original question was "how far inland does a 5 do damage?"
Answer is, it could easily be several hundred miles.
But not as a 5 of course.

I took issue with your statement that with a Cat 4 or 5 that "3 or 4 miles inland -- no devastation".
I guess it depends on your definitions of complete devastation versus no devastation.
Charley taught many Floridians what a Cat 4 can do 25, 50, even 100+ miles inland.
Many of those impacted would call it devastation. I sure would.

Sleep well!

Chris