Just for reference, I'm french and living in France and here is some precisions :

1. The law doesn't allow you to have a knife with you in your car. It have to be stored in the trunk of the car or in the luggage if on a motorbike. But in real life, I never had an issue carrying a leathermann at my belt. If you have it with your tools, you will be fine (My guess is that they wanted to keep your multi-tool for themselves)

2. It is not mandatory to wear a High-viz yellow jacket when riding. It is mandatory to have one in your luggage and wear it in case of accident, break down, etc... If you're on the road. If you don't have one when riding, they can't write you a ticket. if you don't wear one when needed (accident, breakdown...) they will write you a ticket.

3. Speed trap POI on GPS and Waze/coyote is legal in France. But you're not allowed to operate a cellphone/GPS while driving. (if the cops a particularly strict,a running engine can be considered as driving). Anyway, thay are not allowed to search your phone (see the Bonus point below).

BONUS 1 : French cops (Police and Gendarmerie) are NOT allowed to search you or your belonging except if you verbally allow them. They will ask you and you can say no. If you have nothing to hide, you can say yes, that will ease the paperwork checking...
Two exceptions :
-If they really want to go thru your stuffs, they have to call and bring an "officier de police judiciaire" (kind of a judge-cop). They will never go thru that (because there is a limited number of those guys) unless you really pissed them off or if you look particularly shady.
-The border patrol (Douaniers, they are the ones with the red stripe on the side of the pants) can do whatever the **** they want, they are allowed to search your luggage and you by themself, they don't need an "officier de police judiciaire". Don't try to be smarter than them, they can make your life a nightmare of unpacking, repacking and unpacking again, and repacking and so on...

In any case, corruption is really not common here. So don't even try to bribe the cops (it's punishable by law). And as anywhere, if you're polite, smiling and explaining a bit, they might just get interested in your trip and don't check anything at all (particularly the cops on motorbike)

Anyway, I'm sorry you had problem crossing my country, you weren't lucky I guess...better luck next time! (and now you know a bit more about your rights!)