I agree with you, that France held prior to the war a damn awfull lot of gold but I wonder how much of this was already used up for shopping in USA also to the war.
Two cruisers took a load each to North America in March 1940. It was stored in Toronto.
Also I would assume that germany would recall a lot of it by letting France pay dearly for their occupation force in France (part of the 2nd Compiegne armistice).
Did not happen. They got a hold of some scattered bits that were not evacuated in June. The French claimed they had spent it all, & played a shell game as everyone tried to guess which warship/s might have gold bullion aboard. IIRC the French bullion on deposit in the International Settlements Bank In Switzerland was eventually transfered to the German account.
"... and later a large portion of it was kept in Martinique." How much later ? When became Martinique Free France ?
Hard to say. I'm guessing from the start in June 1940. It appears Petains government spread the stuff around so the'd not lose it all at once. Some have theorized the US cruiser that intercepted the Bearn & its escorts in Marinique transfered a load to the US.
Even though the USA kept their diplomats at Vichy in OTL, I doubt that they would have let Vichy act as a Buisness frontman anywhere in the world.
The US policy was to try and draw France away from the collaboration with the nazis by trying to alleviate the effects of the British blockade. That was a narrow tight rope with preventing benefits to Germany. Until the Japanese took control of Indochina the US continued to purchase rubber from Indochina & items from elsewhere in the Fr empire.
With Spain and Franco the story is a bit different, as Franco had also ties to the Allies and no "Free Spain" on his heels. He also managed to rebuff much of the economical influence germany gained during the civil war.
France cold shouldered German inquiries about basing maritime reconissance planes in Morroco, stalled the shipment of Axis supplies through Tunisian ports for many months, obfusicated the transfer of skilled labor to Germany, ect... advantage Franco had was no German army parked in Madrid. Petain had to work with that one.