Question:
Can you abbreviate “Mister” into “Mr.” in a film script?
Answer:
Abbreviations are allowed in character headings (names) and Action, but not in Dialogue.
Any spoken words need to be fully printed, to keep an approximate page count/screen time ratio of 1p/min.
Question:
Does that mean I have to use ‘Missus’ instead of ‘Mrs’?
Answer: Well, err… Technically, yes. But I agree that it may distract from the reading, which may be good enough reason to keep “Mrs.”, even though it takes proportionally less page space than it should.