I'm so sorry this is happening to you, and have totally been there too with a reactive dog on a leash. Here's an article that has some tips on the harnesses that might work for your situation and the benefits and differences between
Gentle Leader or Easy Walk. However, gear alone might not be the solution.
We worked with a trainer and she recommended taking broken up treats with us on walks to sprinkle on the ground around him, since sniffing is a way to reduce anxiety and boost their endorphins. That obviously won't work indefinitely, but as your dog learns that walks are not stressful, you can scale back incrementally. We have gotten to the point now where we hardly need treats to go on walks anymore.
As far as being aggressive with other dogs or people on walks, try and de-escalate things before they get out of control. If you are approaching a stressful encounter or trigger, keep calm, take your dog off to the side and ask them sit for a treat. Having a task to do will help distract them from what might be stressing them out.
Dogs are people pleasers at heart and want to do the right thing, it's just a matter of helping them understand what's expected behavior and what's not.
Hope that helps and good luck with your journey, be patient and consistent!
