Has he always had a short fuse, or is this a change?
Does he think he could stand to get better control of his anger?
Have you asked him about how you might ask him about potential problems in a way that will not lead to him feeling it is a personal attack? What if you have a complaint? Can you agree on a way to complain without it being felt as a personal attack?
For instance, you might say:
"Can we talk? When I asked you if you checked the mail today, I never meant to accuse you or to imply that you had failed or something. I’m sorry that upset you. Still, I want to talk to you about ways I might have of asking questions that you take as attacks. Or, for instance, if I want to do things differently or I do think you made a mistake, how do I make a complaint without it seeming to you that I’m putting you down? You’re a great husband.
You might be able to do something like this
“Did you check the mail today?”
“Did YOU check the mail today? Why are you accusing me of not checking the mail?”
And you say, by pre-arrangement with him at a calmer moment: “OK, stop. What did I ask you? Yes, I said, ‘Did you check the mail today?’ Did I say you were supposed to? No…OK, so I just want to know before I go out. But if you were supposed to and you forgot, do I yell at you? Do I allow you to make mistakes? OK, so let’s start over, and let’s remember that I think you are a great husband who works hard and loves me…Did you check the mail today? OK, I’ll go get it then…and here’s a kiss, I love you.”
You should not have to walk on eggshells, but it may just be that you can help him to “unlearn” negative implications that he heard earlier in his life and now has internalized and projected on to you. It might take awhile for him to “unlearn” the criticism he used to hear and to “re-learn” that you two do not make personal attacks, and when you make them, you take them back. You can complain, but you complain with a problem-solving attitude that says, “I am on your side. I have your back. When one of us makes a mistake, we both cope with it, and that is why we are the greatest couple we know.”
I do not know about the yelling at other people in traffic, because some of the most seemingly mild-mannered people do that. It is like hearing the Easter Bunny snarl at people. I think people allow themselves to do that kind of like they allow themselves to sing the loudest when they are in the shower. They feel they are alone, that they can just let it all out, and no one is the wiser. I don’t know, but other than having little kids in the back to repeat everything you say when your friends come over to dinner, I don’t know how to break that particular habit.
Whatever you do, don’t let this fester. I would avoid making this “something wrong with you that is going to destroy our marriage.” I’d try to make it “we need to learn to talk so we can always talk as friends, even when things are going to h&%$, because the way we do things now is too hard on me and, judging by how hurt you seem when I ask if you’ve gotten the mail, it is too hard on you, too. Life is too short for a husband and wife to feel on edge like that.” IOW, reject the negative situation without placing it as his feet. He is someone who feels accused very easily, so part of your solution will undoubtedly be in making him feel that you might complain but you will NEVER put him down. When he feels safe from that habitual negativity he feels is coming at him (which probably has zero to do with you), then he will be much more likely to let go of flinging negativity back at you.
This is not something you can afford to let him say, “Well, that is just the way I am.” You can say, “You are not insane, and I don’t think I’m quite there, either. If we believe that we each are grateful to have the other, I can learn what makes you feel things are negative and you can learn what makes me feel things are negative, and we can deal with the garbage life throws at us and the mistakes we make together, without getting life’s garbage all over us. Because I tell you, this garbage stinks, I hate it, I think you hate it, too, and we have to do better, or I will go nuts.”