Most of your post points to lack of fuel. But if it started with pedal at WOT, that's usually an indication of a flooded carb, clearing itself and not pulling more fuel in, because the vacuum at WOT/idle almost only pulls air. Could the 0 PSI be because the float needles were dirty/stuck open (no back pressure), flooding the carb? Dirt in the needles is not unlikely if driven for the first time in years. The gauge will only show pressure if a pump creates pressure in a closed system, if the hose fell of for instance, your gauge would immediately read much lower.
Just a guess from a continent away...
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.