I actually never understood, why Sarek and Amanda married. I can understand that Amanda was attracted to Sarek, but it seems illogical that a vulcan marries a human woman.
I am very upset with Sarek about the way he treated Spock. and I imagine Amanda must have been upset too.
Why would Sarek sulk, only because spock decided to join Star Fleet? That's an emotional reaction.
Sarek has always slightly disapproved of Spock's Starfleet career, but the new movie leads us to believe that this is because Spock chose against joining the Vulcan Science Academy. I don't think Sarek ever treated Spock badly, though. I'm not sure where you're getting that. He was always a very loving father, even if Spock's career choice may have initially disappointed him.
As for marriage, why is it illogical for Sarek to marry Amanda? Sarek loved her. She loved him. It also provided a way for him to learn more about humans for his work as Ambassador. I'm not seeing the problem.