I don't know if this is doable, or appropriate, or whether it would help but... the thing that comes to my mind is could the police (or one of them) from your first interview be there at all? They've had dissociation and PTSD explained, they have the evidence, and they sounded kind, so might be able to prevent this guy from potentially trying to bully you? Your current cities' police department is taking you seriously and probably has had dealings with the other one - and discovered that they have a poor attitude in the past. It might be a silly thought, and I don't know if it's possible, but I think I'd want that myself.
However, though he was unhelpful on the phone, now that there is evidence that cannot be ignored, he will look stupid (or corrupt) to this current department if he dismisses it. If it is recorded, then he will look even worse, and your department has the recording, so he is going to find himself in strife if he does not go by the rules (the current department sounds more professional). You have been getting stronger and stronger, you can get through this, you've gotten through much, much worse. (This is what I have to tell myself sometimes). Keep looking after yourself, self-care is vital to keep yourself going, to keep building your strength, mentally and emotionally.