This is why I have a NO EATING IN CAR policy in all our rides.
Insecticides? NEVER PUT ANY

it will definitely circulate inside your cabin and will put you and the family at risk.
The best way to solve this infestation is to
locate the source inside the car which may mean removing the dash as you indicated has the most concentration. Maybe some food found its way into the dash vents. Also try to check the spot in your garage where you park and try trace their steps to their lair because they definitely did not just appear inside your ride, they crawled up via the tires.
Happy hunting!
