A few questions.
Have you ever spoken to "Dad's" WIFE about any of this.
Does she seem to have a grasp of what's happening?
Regardless of his attitude about the man being head of the household,
do you think she is competent and aware of what's happening there?
Is "Dad" your husband's brother?
If so, does your husband feel some responsibility or obligation
because of their relationship?
Perhaps he is used to his brother since childhood
and therefore dismisses the negative behaviors
that you see as dangerous.
Will the only time you (your immediate nuclear family)
will be around "Dad" and his family be during the holidays,
at the home of mutual extended family?
If so, can you have some discrete conversations
with other extended family members.
You referred to your husband's family of origin
as being quite different from your own.
If their cultural/social behaviors and expectations
include denial/avoidance of discussion of problems, etc.,
is "Dad's" behavior/patterns swept under the rug
among other extended family members.
Are you (in effect) alone in your concerns
because you were raised with different attitudes
about openness and communication among family members?
Consider, perhaps, discussing this situation with a therapist
or social worker for some ideas/recommendations
of ways for you to take care of you and your immediate family members
during the holidays without creating a crisis situation.
Please let us know what happens.