Very beautiful car.
According to Google translate:
"podlepit 1mm" = layer to 1 mm. (probably the windshield as you said).
"mezi int. a karos" = "between interior and body"
"drátek" = wires. Probably windshield wipers?
"no clue" = probably the gear stick to be folded and glued? My guess is the same as yours: the single one drawn inside the oddly shaped polygon looks like a template for the profile of the interior. Hence my guess of the small black piece to indicate where the gear stick sits on the floor.
An interesting project. Will follow it
