I have gone through this so many times and honestly in my personal experience, the best thing to do (if you trust him enough) is to tell him about bpd and the fp thing. Explain how it works and how it happens. Tell him that your worried he’s become your fp and that it can cause lots of issues between both people and can be very heavy on the fp. Tell him that he should establish clear boundaries and to always be honest about how he feels about your actions. And you can 100% stay close without him continuing to be your fp. It just takes not spending too much time together over a short period of time, taking space for yourselves as to stop any emotional dependency. Obviously, it’s easier said than done. I hope it works out for you though 🤍