Yes, the Scarlett will just sync itself to the external adat signal. It’s the only option anyway because the Scarlett lacks clock inputs and has no adat output the external device could sync to.

I would sit in the car with some pieces of cardboard and scissors and repeatedly fit the edge of a piece of cardboard to the curve horizontally at the lowest relevant height, then repeat the process at a fixed interval higher up. You can then measure the cardboard pieces to form a mesh.

Checkout Bitwig. It is proprietary, but a professional audio workstation and available for Linux: https://www.bitwig.com/de/8-track/