Sorry to hear you have got yourself into such a corner.
Have you moved in to the new house as yet?
To be honest if he is a pwBPD then you have a long and difficult road ahead of you, and the less complications and enmeshment the better it will be for you to help sort this out. There are no quick fixes
Have you read through the articles below to give you an idea what you are up against?
LESSONSWhat I have found works best when faced with the should I or shouldn't I decisions trying to fathom out what someone wants, is to decide what I am going to do unless specifically requested otherwise. In other words you have a default action mode, rather than live your life pending on trying to work out what someone else wants or really means.
Stay unless he flat out tells you to leave, or make plans to leave unless he flat out tells you to stay. Make him make the choice. Dont try second guessing him.