Bordino and Fines
Try Automobile Quarterly, volume 21, number 4..... the article "Leon Duray, Just The Fastest" by Borgeson.....has some answers to your questions.
For instance, Borgeson met Duray in May 1951, at his home, on "an assignment to do a story on the Fordillac which had just been built to his (Duray's) order,"
They had planned to do some "bench racing later down the line" but that never happened before Duray passed away. So no interview.
And the first trip to Europe ,according to Borgeson, and as Fines explained was to set some records and make some beer money, but also to promote front wheel drive with the Millers and an L29 Cord (also shipped over).
Borgeson isn't sure who financed this "junket"....Packard Electric or E.L.Cord, but thinks both may have been conned into it.
Second trip, as you suggested "an offer he couldn't refuse"...Florio offered $4000 appearance money to Duray for the Monza GP.
Also, in AQ 20/2, Borgeson writes about W.F.Bradley and his conflicts with Duray.