Changing the locks is wise. Setting strong boundaries are important and protecting yourself (and your belongings) is necessary to stay safe. I wish I had been wiser sooner. We lost a lot of money and stuff from our home before we too set security that would not let him in.
I like your reverse Gratitude list. I often refer to "strangely wrapped gifts" which are gifts that we find only after a time of difficulty or after overcoming an obstacle. We see it in hindsight, but it is often there and would not be there at all but for the obstacle that changed our path. Recovery and all the good spiritual changes that go with it, is one of those.