REally sorry you are having all these problems with the PO. I have rarely had any difficulty with them and if I call in to the local office they always transfer me right to the supervisor and it is taken care of immediately. Also I use priority mail all the time and they have never missed a pick up and I can follow where the package is and when it is delivered. I think you should call your local office and gently ask what they think they could do to help you with your carrier.
As far as the material, I would call the sender and ask for advice from them. You never know it might have happened before or it might just be one particular fabric that has the problem. Either way I am sorry your fabric has been mistreated.