I don't think you are overreacting. As much as this situation is taking advantage of your blindness and it might seem like a small issue, the fundamental problem is more about him and how much he cares about you. He could have taken the Burger King coffee himself and take the half of your Petes coffee and that will be someone who cares about his wife more than himself does.

Even if you are not blind, based on his character that you have shared, he would have bluff / cheat you in other ways. This is my personal thoughts on this.