WOW! This is a REALLY hard situation you are in! Talking through this will definately help you! I am curious though, is you mother selling the house ONLY because you are no longer a tax write off for your father? This sounds kinda like a shady situation and someone is forgetting to tell you something.
My parents were divorced when I was 10 (I'm now 22)and my mother got us (all 5 siblings) and my father got the house.
My father does not earn much money, and almost had to sell the house a few times. Seeing the "for sale" sign broke my heart EVERY time, so I know how that feels! He built the house himself. ..the WHOLE thing! And we lived there since I was two years old.
So basically, I sorta know what you are going through. Luckily, my father did not have to sell the house (not yet, at least)and still lives there.
But when you are faced with this situation you have to remember, that although the house holds sentimental value that could NEVER be replaced, life DOES go on. Just try to think that it IS only bricks and wood, and that your family will bring the love from that house into a new house (as it is only a material possession). I know its easy to say, but your family is STILL your family even if you live somewhere new. Maybe the new house will be better in certain aspects and your whole family could grow from this situation. It might just bring you closer together!!! Just remember, a house is just a house, but you can make ANY house into your home!!