No idea on highway tolls in France but you better check.
According to the website
http://www.autoroutes.fr/en/vehicle-classification.htm as a trike it should be the same group as a motorbike.
However all but 1 of the toll booths I encountered last year were unmanned and I couldn't see haw to pay a reduced toll.
At the one manned toll booth after a long argument about whether it was a car or not I ended up paying the car toll:(
