[Gabi]

Not sure if my answer will help you or not.
Not so long ago we rescued a Jack Russell female dog who had then a biting problem. After training, gaining trust, getting her fixed etc she calmed down....but ....like yours I don't trust her much when we're out and about.

I bought 2 things for her that fix the problems quite well. One of them is called "halt". Its basically a device you put around the neck and around the nose and she can't pull anymore at the leach. It doesn't do a thing as long as she behaves well. But soon as she pulls, she pulls her head automatically towards her breast. And it works as charm. It stops her pulling AND aggression same time. When dogs get nasty they pull also. Breaking through that stops the aggression. Added plus is that you do have also in situations like that control over your dog.

The second device I bought for her is a muzzle. Because I can't trust her in certain situations, she gets the muzzle on and done.