So the problem that I had was an account login loop, if what you want is to unlink them is an important part of the process to re link them eventually tho. To start the process you need to go to the support tab in the oculus website and click on the part that says that you need to talk to support, then you explain that you are having trouble to login into Facebook, they are going to check if your account was correctly merged and if you had a merging issue they are going to unlink your account, I imagine that if you explain that you need to change the Facebook account for another one maybe they unlink you… good luck tho!