It is a pretty barebones port, so it is apparent Square Enix didn't invest too much into it. So I don't see them investing in localizing the third game just for this Switch port.
I can read it to an extent, and there are times when not being able to understand it fully hasn't stopped me. I may wait until the price goes down before I import it, though.
Probably not. They'd need to translate the third one entirely since it never came out of Japan before. I think they were just hoping for a simple port with little effort to keep the switch going until the next game hit.