Πρέπει να βιαστώ.

As this is passive voice, I wonder if the Greek should be
Πρέπει να βιάζομαι

Hi - πρέπει να βιαστώ is correct. Να βιάζομαι would be the continuous passive, with να βιαστώ being the aorist / perfective passive. I think that the continuous can be used in the right context (see Glosbe) but να βιαστώ is better here.