not knowing details I can only tell you what I do, I bore myself up, be as boring as possible, stop posting pics, stop doing things publically, go watch a bunch of movies for a few weeks
I have been in your shoes and ar first i was trying to be nice to this person despite the toxicity but i ended up really anxious and started to even hated login in so...mute him change your profile and hide groups, change the location of your picks...stop hanging where he knows you do.
Make an alt if needed and tell only the people you want to be near with so you can still be in contact or hang out with...if he makes alts to contact you...mute them. You do not need to stay or to be nice to this person. It will be a bit hard but it gets better.
ZieklingKeishiiRoo this is definitely the way it’s gotta go, it’s gonna suck and be super hard. Thank you so much for the advice it really has helped me