It sounds as though your anxiety won't be helped by any simple solutions, such as the pet spray sold in many pet shops. Your dog will be picking up on the anxiety as it travels down the lead. Have you thought about working with a behaviourist? They will give you advice on how to remain calm, so you and your dog can enjoy walks together.
As for the Rottweiler, one problem is that dog on dog attacks are not usually police matters. it would be the local dog warden who would keep a careful record of any incidents. A neighbour was recently warned that if her dog wasn't kept under control, she'd be taken to court. the warning was effective. She got a trainer in and the dog's behaviour improved a lot. If a person has been injured by the Rottweiler, that is a police matter. They can investigate under the dangerous dog legislation.
I'm a two or three dog household. I'm increasingly careful with my own well behaved dogs. Lockdown has made our usual quiet walks much busier, its great to see so many people enjoying our countryside. However, many of them seem to have uncontrolled dogs, that have no idea about recall, or simple good manners. The allow their dogs to run up to children and other on lead dogs, often shouting "he's friendly". I responded to one recently, maybe, but mine is a killer - call your dog. Needless to say, the dog didn't recall and my big soft dog behaved perfectly (she isn't really a killer honestly)