Add this to your plan.
If he shows up at your house to see his son and he is 'off' in any way, call the police. This will get you a police report from and is called CYA as they will either agree that he is on something or say no he should not be around his son at that time. You then get a copy of the report and give each and every one to your attorney as I am sure it will happen more than once.
That will go further toward your attorney being able to get 'supervised' visitation for your son.
J M H O
Love and hugs,