Could acupressure cause facial pain from the trigeminal nerve?

Possibly. It is possible if the nerve is irritated. You may need to go to the doctors to be evaluated to make sure you have normal nerve function.
Probably. While i've never heard of this happening, i'm sure it's possible that pressure on the area right in front of the ear (where the trigeminal nerve comes out) could irritate the nerve and cause pain.
Possible, unlikely. Possible but unlikely. See orofacial-TMJ pain specialist for exam/diagnosis.