Pleasing one's husband

Q: I just want advice regarding my husband. Don't know what to do. When I go out with him even when I smile at a cousin brother, he gets annoyed and tells me I am committing a sin by smiling at men. Please advise me what is right and wrong.

Studying to become a physical therapist

Q: I am a Muslim (guy) college student. If I study to become a Physical therapist for the sake/pleasure of Allah:

a.) Will Allah accept it?

b.) Does my going everyday to school become a worship (Ammal)?

c.) Does my studying of major subjects,exams,quizzes day and night become a worship?

d.) Can this become a source to gain the pleasure of Allah? And also can this act be included as one of the good deeds that can make me enter Jannah?

Taking an oath that one will become a kaafir upon doing a certain action

Q: I have heard that if a person takes an oath that “If I do this or do not do this, I will become a Kafir forever”. The person becomes a kafir if he or she swore the oath with the belief that he or she would adopt kufr upon its non-fulfillment. Is this true? I would be very grateful if you could please provide a detailed answer for my satisfaction.