I feel for you, having a reactive dog is like taking point on a military mission in enemy territory sometimes, and other days it is a pure pleasure to walk -- you just never know.

Perhaps the muzzle you have chosen for him was the wrong fit, this video can help with choosing the right muzzle. Then you can acclimate him to wearing it. Here is a long version on muzzle training. The idea is to make it fun and delicious!

My guy wears his muzzle on every single walk. It just isn't worth the stress for him not to. Also, it protects your dog against false accusations of biting and protects you from a potential legal action.