Oh, this is really a terrible situation. I understand how much work needs to be done to fix the roof. First of all, do not worry, this will not help the cause. I was already in a similar situation, so I can say that your problem is quite realistic to solve. Just hire good builders and everything should be fine. I can also advise you this calculator for roof slope. At least it will help you to better calculate your new roof pitch. And good luck, I think you need it.