So today after she got home, we discussed it a little more and she says that she wants to work on it. However, the way that she interacted with me was a bit rigid and distant. I feel like an emotional wreck inside, while it appears to me that she is perfectly calm and almost indifferent. She didn't initiate any physical contact, didn't refer to me by a name (it's usually a pet name), and is a bit terse. I don't know what tomorrow brings, but I am dreading being alone with those books.
She's angry. What you described above is what an angry person is like. Making decisions out of anger is almost always the wrong thing to do. IMO, counseling is a great idea. You both need to go -- together and individually. Let me ask you something, and you don't have to answer if you don't want to, but just think about it -- you said you have a bad temper. At any time, have you ever struck your wife when you lost your temper? Have you ever cheated on her? Have you ever said something to her just to hurt her, something that you knew would crush her to her core? If the answer is yes to any of those questions, it may take a lot of work and a very long time to heal those wounds, if it's even possible, and I doubt you'll be able to do it without a professional helping you.
If the answer is no, I think you're in a much better place once she gets past her anger/grudge. But the way to do that isn't to tell her to change her ways. If you feel that she has a right to be angry at you, then I think you need to acknowledge that and take full responsibility for what you did and tell her you realize it'll take her time to forgive you and trust you not to hurt her again, but that you'll be right there for her when she does. And in the meantime, you need to prove to her that you've changed, even if she continues to hold a grudge for the time being. You can't promise to change under the condition that she get over her anger. That's not fair. You need to change first, and then she can decide whether or not to offer forgiveness (it's like if someone cheated -- not saying you did, but just as an example -- the cheater can't say "hey, I'll never cheat on you again as long as you forgive me." That may not be how he/she actually means it, but that's how it's interpreted by the non-cheater and it just leads to more hostility. The non-cheater is probably thinking "How do I know I can forgive you until I see proof that you've changed and you're the same man/woman I married?")
With that said, there's a however here -- if you feel she's angry at you without reason or that whatever she's angry about isn't justification for how she's treating you, then that's a different story and something that needs to come out in counseling.
Now, as for Step 1, when are you required to take it? Will your school give you an extension? I would continue studying, but you also need to work on your marriage. No Step 1 score is worth sacrificing your marriage, if you still love her and want to make it work (and it's obvious that you do).
Does your wife work? Can you study during the day if you know that when she comes home, it'll be together time? Set up a date night. Ask her to dress up, but tell her the reason is a surprise. Make reservations for dinner, buy her flowers, take her to the theater or dancing after dinner. Show her that you still love her as much as you did while you were dating. Make it a once-a-week thing and show her that you're willing to put in the work to save your marriage. That may go a long way in proving you still love her, despite what went wrong.
The caveat to that is don't be a doormat. Let her work through her anger and all, but if it's clear she isn't interested on working things out, you'll need to re-evaluate the situation. If she genuinely still loves you (and I'm of the opinion that you don't always have to be "in love" to have a happy marriage -- passion comes and goes so long as you always love your spouse, assuming it wasn't the passion alone that drove you to marriage), then I think you'll be on the upswing if you can work through the past.
Best of luck to you and don't apologize for posting. We're here to help
did you cheat on your wife? if not, which I bet you didn't, your wife is behaving in a disgusting way. she knows that you'll be in a lot of pressure because of your exam and still treats you like **** and tells you these horrible things that she knows that make you feel sad. STOP GIVING GER ATTENTION NOW! she's showing distant signs. lock yourself in the room studying and wait for her to be nice. don't rush nothing. if you pay more attention to her than to your studies she will continue to treat you like ****
Divorced or unmarried? Either way, OP, don't ever listen to this kind of advice. It obviously comes from someone who hasn't been where you are.