You have to tell him in no uncertain terms that that has to stop immediately. I would lose my sh#t if W just showed up randomly at my house, or even worse, was already there when I got home. That is cake-eating.
When my W left, she took the moped and I kept the car. It has been really cold recently so last night I was going to give her the super thick winter gloves for the moped which she had left. However, I discovered that they were already gone. She had grabbed them one day when she came over for the dog. I calmly but assertively told her that she isn't to take anything from the house without talking to me first. We need to lay down rules for how things are going to work and simply let the WAS know that is how it is going to be.
Also, I have to agree with Ovr, that it IS none of his business where you are or what you are doing. You don't need to be hostile in your responses, not at all. But you don't owe him any explanation.
W 34 Me 42 Married 7 years together 8 0 kids 1 beloved dog BD 4/6/2018 I moved out 4/7/2018 I moved back in alone 8/05/2018 I file 3/06/2019 D official 5/7/2019