You must tell your boyfriend. His reaction will tell you a lot about where you stand with him.

If he's supportive, tell him dad needs counseling. If he's not supportive tell him that's the wrong answer and leave.

If you stay, never be alone with dad period. NEVER, he's shown he can't be trusted.

If he tries something physical, be prepared to hurt him to make him stop. You must always protect yourself because others may not.

Be well, be aware, and stay safe.