Hi Zoe,
So sorry that you are going through this with your partner and his coke habit. if you would like some help for yourself please contact us at Icarus Trust as we are a charity that supports people dealing with addiction in their family. We have a team of trained Family Friends and one of them would talk with you if you get in touch. Maybe that would help you to answer your questions and see a way ahead.
You can get in touch on contact@icarustrust.org
Good luck.