There’s a lot here to respond to in your post. First of all, are you safe? Are you making sure he cannot access your device that you’re using here, hopefully in privacy mode?
Do you have a go bag hidden with essential items such as money, credit cards, medication, extra glasses if you wear them, documents, change of clothes?
Please take the Mosaic test, a survey to determine the level of risk you are in regarding your relationship and let us know your score.
Mosaic testYou are wise to not jump into a marriage commitment right now. Often that can exacerbate BPD behaviors, which you’re already seeing. Regarding meds, unlike a bipolar diagnosis, there is no medication that completely treats BPD. Some meds can help with depression, which can certainly lessen some BPD symptoms.