Hi MWG, I think this is going to be hard for you to do, as you have always been there for him when he comes and goes and it will go against your natural inclinations but I hope you can do this for your sake and his.
You could be here 5 years from now with nothing changed and you need to do this for your own health and long term well being.
You have given him "the word" he apparently knows it and still chooses this path, so you are scriptually correct in "shaking the dust from your shoes" and leaving him be.
Jesus told his disciples to do exactly that if I recall correctly.
You still working at the shop you haven't mentioned it in a while.
I hope your week end goes well. Stay comitted to your plan.