Dear Stuck,
I am a Business Coach, and I spent many years in a family business. I would like to find a counter argument and tell you you why you should stay,  but I I can't find any. My biggest concern is that based on the way this family business is run - I am concerned about the future health of this business. 
Please keep in mind that it's best to leave on your timetable and on your terms. Do not fall into the " out of the frying pan and into the fire trap". Learn from this experience. and try to be more aware of the culture beforehand in your next job.
I wish you the best!
Phil