I also had a Demon ( proper name.. I did eventually "exercise" it from my car ) that had a VERY similar problem.
Constant flooding, did alot of the same thing, crank the idle screws closed, added a regulator, continued to lower floats, on and on.
It got to the point I said enough and pulled it off and pulled the fuel bowls.
The float has a tab that as it rises pushes the needle into the orifice so as to stop fuel flow.
Well, the tab was not bent correctly ( mind you this was a new from the box carb that I had never taken apart )
so even with the float in a full bowl/closed needle position, the needle was not & would not seat to close off the flow.
After a quick "tweaking" and reassembly, we were set.
I know it's not an option for all, but the straw that broke the camel's back for me was when I had the throttle set-up to open WOT when the gas peddle was fully depressed the linkage on the carb would do as I can best describe as a "flip" and lock the linkage in a WOT condition.
You can guess my surprise & anger after that.
Good luck