Any chance it is a resolution/ratio issue? Be interesting to see how it works on the mobile display.
If I understand your explanation and your goal is to put the VIM3 to sleep with the key-off, sounds like it should work. I would check VIM3 power consumption when it sleeps to insure that the resulting constant drain on the vehicle’s battery is tolerable over time.
On the Pogo pins, I was thinking a piece of perfboard big enough to span the mounting holes in the VIM3’s PCB and the XPWR pads location. Mount Pogo pins to perfboard and attach leads for switch/relay. Perfboard mounts to VIM3 PCB, engages Pogo pins. If the relays are small and the perfboard large enough, relays and other component could all be mounted to the perfboard. Of course, some measuring would be needed to determine the length of Pogo pins and the spacers/standoffs hardware used to mount the board.
Though a case with the pins would be cool.
VIM3 cannot be powered over GPIO, see here.