I do sympathise with your problem jourdain. I agree with Woofy you need help and I would say a Dog Psychiatrist is needed, definitely not a job for the amateur. If you are near Surrey/Sussex I can recommend one.
The trouble is with putting a muzzle on it doesn't solve the problem as the problem will still be there when the muzzle comes off. I understand why you use one though. Same with walking where there are fewer dogs when actually you should be walking where there are plenty of other dogs so your dog gets used to them and they to him.
On a practical note, when you see your dog showing signs he is going to attack another one, call him to you and give him a treat holding the treat in your hand until the other dog has gone past and then give it to your dog. Make the treats special, and really small, so he wants more. In other words take his attention away from the other dog. poor dog obviously has fear aggression. I can't advise on the other problem, that is up to the owners of the attacking dogs. Good luck Jourdain, it's not easy. X