In all sincerity, it sounds like this relationship has run its course. Rarely, can a relationship come back and be healthy after this baggage. I know it hurts. But he's trying to keep his foot in the door, not fully let you go for his own insecurities. You don't need that. I would break ties. Not in a dramatic way. This has all been a little volatile. I would keep your dignity and quietly move on. I would cut off all ties. Do not respond to anything he does, tweets, messages you, etc. Not to keep the drama between you going but to heal and move on. We're here to help you.
Things that help during a break up: staying busy, picking some things to work on for you like work, school, exercise, a hobby you enjoy, keeping a journal for emotions. And know that time heals. I went through a painful break up and later met my husband. Married almost 20 years. Could not in my wildest dreams imagine being with the person I was broken hearted over. So, this will happen to you too. hugs
He sounds really emotionally manipulative. "You can still come to me for advice" is to preserve your nice guy image of him, and is just to make him feel good about looking like a decent person. The sad instagram post is also to manipulate your thoughts of him. This is honestly a really tough thing for you to go through, and I suggest *completely* ghosting him. Remove his ability to check in with your life. Block him on all social media. He's going to be so frustrated knowing there's someone he CANT manipulate anymore, so use that to jumpstart your journey forward without him. Don't involve him in your healing process if possible, because its going to feel amazing when he sees you a year later, in passing.