Sounds like you have a lot invested in this place (volunteering with blood drives and all). It's very easy for all of us to say "go somewhere else", but I know that isn't always an easy thing to do. I am so sorry about the loss of your son
I would think they are just trying to get you to accept less pay, and using legal loopholes to do it. I agree with consulting a lawyer, especially if you don't want to move elsewhere. I have never left here because this is where all of my social support is (also had a death in the family), even though I could probably do "better" elsewhere.
My hospital really hit the skids some years ago, working conditions were horrible, but we as a nursing union did something about it. It is possible to fight for change from within. If this hospital is where you want to be, fight for it. God bless, and let us know what happens.