Confusing situation with ex... i dont know what i should do?

My ex and I started dating two years ago. Everything was okay in the beginning until he became abusive, and grabbing my phone out of my hand to check who's texting me, contacts,etc. I was cheating on him also so it was a toxic relationship overall. So I decided to leave. I cut off all contact with him, changed my phone number, work place, got off facebook. A couple months later, I was at my friends house and she insisted I make a new facebook, for my other friends to keep in touch with me. So I did. Next thing you know, my ex finds me,sends me a friend request and a message asking how im doing and asking for my new number. I gave him my new number after days of him begging me saying he wants another chance. After I told my best friend what happened, that he came back to find me, she told me to ignore him and block him from my cell phone and facebook. So I did. Then, since I blocked his texts, he calls me saying he misses me and "thinks we could be good friends" and that "he thinks im the most beautiful and cutest, that he wants to sleep with only me, that I can't be replaced, and other sweet things, I kept hanging up on him. Sadly, I must admit, I do have leftover feelings for him, but I am scared if I allow myself to be in contact with him, that he will seek revenge for me cheating on him in the past? how can he be so charming and sweet after all the things that happened between us? he never gets mad anymore on the phone, even when i ignore him, he is just so persistent to see me when he used to be so abusive before. I am really confused and I need helpful advice on what I should do about this whole situation please and thank you