What type of work ethics is this???

Recently I have been having some problems at work and I had a few questions I would really like answered. Ive been working for this company 3 years now. When I started working I was in our Tokyo office. About 1 year later I was transferred to the Irvine CA USA branch. At that time the agreement that had been made with me on terms of pay was that i was to receive 70 thousand a year based on salary. 1 year after the transfer my general manager informed me that I was going to get a pay cut based on my "performance" not wanting to leave the United States I agreed to the pay cut. My geneneral manager and I have never gotten along because a "lack of communication" and that being that i would not be a mindless drone and let him take credit for my work. This all transpired about 1 year ago. About 3 months ago my general manager informed me that a member of my staff was to be promoted to my position and that I would be demoted and once again a decrease in pay. I am now doing my old job in addition to her old duties. Now they are saying that they are thinking about sending me back to the Tokyo office if my "communication" skills dont improve. I have been a hard worker for the past 3 years and many people think that I am overqualified for what I do. My boyfriend recently asked me to marry him, and this concerns me because if my company wants me back at the Tokyo office our relationship won't work. My questions are... 1) Am I being discriminated against because my boss doesnt like the fact that I have high working standards and wont do things and attribute to his credit. And question 2)Am I being retaliated against on the sole fact that when I started in the US office my salary was higher than his? Also the sheer fact that he does not like me as a person or a worker? And finally question 3) would it be considered as "just cause" if I quit my job because I am soon to be married and dont want to ruin my relationship with my boyfriend?