If I remember rightly he has repeatedly set boundaries that you can't work with and has been clear he doesn't want to have contact with you between med refills. I'm wondering what you think writing to him wil achieve. He isn't doing therapy with you and so isn't your therapist - I doubt he'll be in any way bothered at your decision to move on, which may sound hurtful but isn't intended to be. You need much more support than he can provide you, it would be an act of kindness to yourself to stop trying to get a reaction from him and find a service that wants to, and is able to, meet your needs.