B&B.....
I think that the best and most thorough list is the one that you make yourself. If the reasons that other people thought you should stay away from him worked you wouldn't be worried about needing this now. I bet that the people that love and care about you have given you a number of reasons through the years (I know that I got a lot of them) and none of them made a difference until I made them, owned them, accepted them.
I found that the reasons why I needed to stay away weren't as helpful as having a plan for when I heard from "him". The plan included not responding to him without first talking it through with people in recovery. You might even say "I won't respond to him until I post about whether to respond or not on SR and wait for 10 people to respond". I had to put him to spam, block him on facebook, and block him on my phone. That was the best way for me to avoid hearing from him.
IMO, if you are still making that list of why to stay away you might need to place some more barriers between the two of you. Get a game plan for how you will handle the inevitable running into him or contact from him. All of the reasons in the world to stay away won't help you nearly as much as a list of ways to avoid him if you have truly made your mind up about this.