First, dare I say take a chill pill.
I know this is important to you but you are taking this WAYYYYYY too seriously. Your frustration may and probably is rubbing off on the dog and causing some of the mishaps. Other mishaps may be because the dog isn't having fun or isn't getting the pleasureable response from obeying as she once did. Take a step away from training for a while, have some fun with her and practise building or rebuilding the bond between you and her first before you go back to training. Perhaps she will never be the perfect 'stayer' or 'obeyer'. Accept that and be happy with what she can give you at any moment in time. Dogs live in the moment and sometimes that moment doesn't correspond with our plans. LOL