OP, something to try.... drive, shut off, heat soak as usual, pull air cleaner with engine still shut down, operate throttle and check for pump shot. If exists, repeat two or three times for consistency.
Unfortunately, Demon's don't appear to have fuel level windows and the carb must be removed and upended to remove the cover. I usually check my 4100 by pulling the top cover off. Easy to see what fuel is in there. Holleys have the windows.
If no fuel exists in the carb, it's boiling out from the heat soak.
It sounds like you're losing fuel supply when shut down and it won't re-engage. An inline fuel pressure gauge might lend some clues.
IMO, do a thorough diagnosis before making any more changes. In the past, if I'm thinking the carb is involved, I'll even swap in a known good carb for comparison. You'll find the problem eventually.
FWIW I ran the race car for decades with a Holley blue pump, aluminum fuel line and a short braided to the engine with the only insulation in the header area to protect the hosing (vastly different routing from OEM). Never a lick of trouble. With that anyway