uRGENT Crisis!!! Please help!!

'll try to make this long story short:

I have been studying myself and the world for some time now and have changed many of my world views. At this point I no longer consider myself muslim as my family does. I am a south asian (living in North America) and althgouh in my early twenties, live at home with my parents because I'm required to by tradition.

I live in a rather dysfunctional and somewhat abusive family as my parents have very strict and narrow minded requirements for us (such as having no contact with the outside world, having no friends, spending our life obeying and never questioning etc.)

My life (and that of my siblings) is composed of short periods of 'good times' followed by long periods of severe verbal and sometimes physical abuse by the parents, most of the times for something as simple as not getting having too much or too little salt in the food (I cook).

We never disrespect them while they go on because deep down, we know that it's not really their fault they are this way. They came from very religious and severly dysfunctional families themselves. It has now come to the point that they are asking (forcing) me to marry a muslim boy of their choice.

I have a Catholic boyfriend and we are very serious about each other. After much talk and debate, we decided that he would 'convert' just for them (in reality neither of us belives in the religion, so it would be just to make the folks happy).

I told them about him for the first time yesterday and they got extremely angry, I feel lucky to be alive right now. They now tell me that I either have to convert him and marry him and then leave home and never show them my face again (they would disown me), or I have to marry the guy they want me to AND do it with a smile on my face.

They are also very serious about telling me that if I go ahead and marry my boyfriend and he doesn't convert, then they have a God given responsibility to kill me (literally murder me) and they will do it no matter what they have to face for it!

My question is, what am I to do in this situation? As bad as they behave towards me, they're still my parents and I don't want to hurt them by leaving. On the other hand, I can't marry the guy they want me to, not just because of my boyfriend, but because I do NOT want to live my life being muslim, and I will NEVER bring my children up under this religion!!

I believe that we all choose our life path in the time between lives, and do it based on the lessons we want to learn from the life. I just wish I could figure out the lesson I am supposed to learn from this? Which is more important? My beleifes and principles, or the feelings of those who brought me up? Any opinions?