Prescott Fond Blanc Melon
The typing is getting garbled for me in your big, long thread, and I can no longer leave a response. You asked if the advice of the French seed company to only leave one fruit per plant would be a good idea.
The melons of this variety which I have picked so far have all been crown set melons - tight to the base of the plant. If you had more than one there, they could possibly get deformed because they would get squished together.
Once melons start to set further down the vines, I wouldn't worry about having more than one at a time. My plants haven't been setting all that much fruit.