Facebook glitch... I am currently ignoring someone on messenger, I have restricted them.

They started reacting to my posts so I hid my posts from them. Now it appears they can still see, when I try to hide them again their name isn't available to click. This is causing me distress, I don't know if blocking them is an option. They are a Narcissist apparently and I think they are using me to get at the people they fell out with (long story) it feels like he's homing in on me and also feels creepy. I swear this person had disappeared from my friends list and is there again as if they have reactivated.