Hmm, the questions strikes a chord, given I’ve been there (a long time ago), and later on the other side. So this is going to be a long answer. ;-)
It’s probably easiest to split the question into the different issues raised, and the perspectives involved.
As you have found out by now, anonymity is really difficult to achieve online. My guess would be they recognized the writing, esp. if you became noticeable during the course (class size doesn’t matter then). But identifying students is even possible if there is only numeric information, and if student votes are aggregated. However, just because it’s (easily) possible to identify students, it doesn’t mean it should be done. If anonymity was promised it would be highly unethical if they would identify you by the evaluation itself. There are two conditions in that sentence. First, was anonymity actually promised («allegedly anonymous»)? If you only assumed it would be anonymous, because you don’t sign it, you have no right to be surprised. Second, unless they explicitly make the connection between you and the evaluation, it’s an assumption that they have identified you. Other explanation: You criticized the course, they might have gotten a bad evaluation and want to find out how to improve. But if both hold true — anonymity was assured and they do identify you as the author, then it would raise a huge red flag about the people involved.
(It's a bad idea to give a «scaredundergraduate» a virtual gun, but if the highly unlikely case happens and the conversation turns actually hostile, and you are in a one-party consent state (look it up!), it might be an option to secretly record the conversation. This is a «last measure» option. Personally, I think recording without the other person knowing is a major breach of trust — reserved for criminal acts, no matter the law. Any relationship and any trust is irrevocably broken if you do it — and I strongly advise against it. The idea of a meeting is to resolve an issue without anyone losing face. A recording blows that option out of the water. The conversation would really have to go downhill to think about using, e.g., the laptop you took out to read what you have written and record the conversation.)
Also, I wouldn’t expect hostility here. It’s much, much more likely that they want to resolve a very unhappy situation for all involved.
As others have written in comments, it is better to stick to the facts and take emotion out of it. After all, it’s about the issue and anonymous comments don’t hurt less than comments made in person. Even worse, it raises questions about the person who makes anonymous comments («coward» comes to mind). Frankly, after some ‹learning experiences›, I go with «If you wouldn’t say it in their face, don’t say it at all.», combined with «If you snicker while writing, it’s time to pause and reflect.» However, you’re not the first person to whom this has happened and while you can’t change what you have written, you can still control how you deal with it. It’s painful learning, but given you ask the question here, you’re on the right track.
From their side, it depends on how they deal with these type of comments. Some instructors take it personally, others chalk it up to inexperience. You are a student after all. If they are professional, they might talk about they style and that it’s not conductive to improving the situation. Imagine you’d gotten this evaluation, would you have changed your behavior? Seriously? There might also be misconceptions about the course involved, and there is also the responsibility to avoid having students leaving one’s university/course and thinking this style is good practice.
Issue #1: Class Content
When it comes to the issues you’ve mentioned, I think it pays to go into the conversation with an open mind and listen to their point of view. I once had a student who wrote a scathing paper about a course, seeing everything in the worst possible light. There were a lot of misconceptions about the academic world in that paper (e.g., thinking my colleague and I were like full-time teachers and we were only giving two courses and had the rest of the week off). Once she did understand what we did the whole week, she saw things a bit differently. My guess is that «took a long time to grade our assignments» might fall in that category, but I might be wrong.
Other issues like «too easy» and «standards were too low» might be individual problems (you might just be in the wrong class). However, you also write that the class is a prerequisite and if you are not learning what you need to succeed in another class, then this is an issue to talk about (and focus on).
Issue #2: Interaction with Instructor
I would differentiate the issues with the content from the issues with the instructor. Again, his perspective might be interesting to know. You interpret his comments («I have to do this the hard way now since [me] will see the handwaving.») negatively as «you’re a spoilsport/know-it-all». However, even if you cannot phantom it otherwise, the intention might have been different. Social interaction is messy.
And yeah, perhaps this person is not competent to teach the course, but perhaps he adapted the content to the average student. Perhaps he will take the anonymous criticism very negatively, perhaps he understands your point of view. And perhaps a skillful mediator can make both sides to see the issue from the other perspective. In general, you don’t have to like the guy, but you have to work together professionally. And at least on the learning side, this seems to have worked out well. Some improvements are necessary on the «you can say anything, as long as you do it respectfully» side.
In situations like these, you can’t undo what has happened, so it matters how you deal with them. So, first, chill. Yup. Chill. You’re in a situation which nobody wanted, and that is something nobody can change. Pretty much the worst that can happen has happened, so chill. And yes, you did act badly, but you can still act with integrity in how you deal with it.
A way that might work (social situation, depends on all involved) would be to focus on the actual teaching issue — the content of the course and the interaction with the instructor.
What you have going for you is that you are passionate about learning (even if it’s only for the next course) and that you have mastered the content. That this passion leads to frustration if you don’t think you can learn what you need is understandable, as well as the style. If I were you I’d go this route. You wanted to learn and be challenged — and the course was very frustrating to you.
On the negative side, I think your interpretation of Dr. Smith’s behavior as hostile (and unfair) has strongly influenced your evaluation. When it comes to him, focus on the actual observable behavior, not the person. You don’t know him and it would be arrogant to assume you can characterize him as a person based on your limited interaction in one setting. Plus you can change behavior, personality not so much.
In general I’d go with assuming the best case, both sides want to find a good solution to the unhappy situation. Take a deep breath, go into the situation, let them start the conversation, focus on the issues, listen, state how you see the situation as your perspective (not as «fact»), and on the emotional side that you were frustrated with the course because you want to learn and be prepared for the next courses. As for the style, an apology might be in order if you actually feel this way — because you were frustrated with the course and wrote unprofessionally, not because the anonymity was lifted. It wasn't constructive, and yeah, it was wrong. It feels good emotionally in the moment, but it further complicates the issue and is likely unfair to the instructor involved.
Best outcome, you might end up understanding Dr. Smith’s behavior (perhaps it’s not hostile/unfair), and they might get some constructive feedback on how to improve the course.
BTW, an update would be appreciated how the conversation actually went.
Edit: Some pre-coffee spelling/wording mistakes.