Actually, the changed terms of your CTC contract is legal because it is "real airline world" training for the future when you are at an airline and your T and Cs change monthly. I believe the ATPL is going to add another subject called, "changing terms and conditions".
Honestly, buddy, I'm sad to hear your misery with the finances. They know that you have come so far and spent a load of money, so they are banking on that you won't throw in the towel while being so close to that shiny jet. So, really they played everybody beautifully because your screwed if you don't accept the new terms and screwed if you do accept the terms. Its win-win for them.