I think that you have a good chance of retaining the custody that you have since there has not been a considerable change of circumstance.
Keep the letter, the e-mails and the DVPO paperwork. This all shows that he is flat out lying about not providing the address. Once this is established, it will throw a little doubt on the rest of his claims.
If you are divorced, you are under no obligation to provide a name of a roommate, romantic interests or employment. You do not need to provide him with information that does not involve the child. You are no longer obligated. See if you can get transcripts of the Sept.2nd hearing where his attorney was told you did not have to provide a name.
If you are communicating via your cell phone, request a copy of the call log. Your request that he not text you is valid and since your son can not read, you may get a slap on the wrist for not communicating his father’s sentiments to him from the text, but it’s not an issue. You are allowing communication and even providing him with more that he has refused to accept. Save all communications to this affect.
Not a real good chance, especially post divorce, that this is going to happen. Your roommate is in law enforcement, with no criminal record. Your ex can not dictate who you associate with and there is no judge that is going to remove your child from your care because you have a roommate (not boyfriend, roommate) of the opposite sex. If your roommate were to be found to be harmful to your child then it would be a criminal matter and your ex would still have no say over who you lived with.
Custody is normally modified due to a change of circumstance that no longer benefits the child’s best interest. Your having a roommate of the opposite sex and not allowing your ex access to all information about your life aside from the child, is not cause to have custody modified.
If you had an attorney for the original custody you should look into using the same one. You could have the attorney request that he pay the fees if it can be shown this was a malicious suit…