Pass is right about not saying anything about going dark. I struggled with that too. You want to tell them why you are doing it. Why? It will only come across as controlling or weak.
Just go dark...
And don't do it expecting some reaction from H. Most likely you'll get one but don't sit there with expectation for something...
Going dark is for you...it is a necessary stage in detachment IMO and when you come through it you won't need boundaries anymore...you'll be free. You can handle your H in any circumstance with loving detachment.
BUT...
It is HARD. You'll have to fight yourself for a while to do it but do it you must...
My goal is to some day be the person my dog thinks I am