Some how, some where, deep inside you, you have to step out of your self and look at your parents as a stranger would.
If you were a stranger to them, you would not allow them to use guilt and pressure you into giving them what they want.
As irrational and impossible as it sounds, they are not loving you as a daughter, but as a person that helps them satisfy their now childish demands.
I have been reading this thread for some time, and am not surprised when you report how cognizant they become when the change of guardianship was announced. I see patterns that help them maintain their 'status quo.' no matter what it takes, or who they hurt in the process to achieve that status.
Sometimes our loved ones become people we don't even know. The why, has no satisfactory answer. Your folks are enabling each other, and they see no reason to stop that behavior.
You have an upcoming goal in your education that will be a life changing event. Do not let your parents selfishly take that away from you. They should be encouraging you to beat the band, dropping balloons and cheering from the rooftops.
As I'm old as your parents, I'm stepping in to say..."GO FOR IT. YOU GO GIRL, YEA FOR C4C, go ripping in there and get that dissertation finished. When you have completed your work, there will be time to revisit all of this, if you wish. Otherwise let the stream take this upset under the bridge and out to sea.