Is it permissible for a resident of Ta'if who works in Rabigh (320 km away) to break his fast while traveling, shorten prayers, and combine them during his weekly vacation days (less than 4 days) spent with his family?

Firstly: The travel distance between Taif and Rabigh (320 km) is a distance that permits shortening prayers (qasr). Therefore, you are allowed to avail yourself of the concessions of travel, such as shortening prayers, combining them, and breaking the fast.

Secondly: One who resides in a country for work with the intention of permanent residency is subject to the rulings for residents in that country. Thus, he must fast and complete his prayers. However, if he subsequently travels to his hometown or a country where he has family, and does not intend to stay for more than four days, then he is considered a traveler and is entitled to the concessions of travel.