Is enough becoming enough?
No. These questions are technically on-topic, though I would definitely agree with you that they are poor quality (a simple Google search answers some of these, and most of the others can be found with some additional research). However, you need to keep in mind that on SE, there is a strong difference between closing a question and downvoting it. Closing a question implies that the question cannot or should not be answered, because it is too broad, unclear, or simply not something we cover on the site. Downvoting a question implies that the question is poor quality or not helpful to other users. There are questions that have many upvotes that are closed for being off-topic, and there are also questions that are not closed that are heavily downvoted.
If this user continues posting poor quality questions, the system will eventually catch on and question ban him.
Am I the only one annoyed by this?
No, you definitely not. As much as I'd love to smite some of these questions with a close vote, I refrain from doing so because, as I explained above, that would inappropriate. Instead, I have to settle for a mere downvote which, although perhaps less satisfying, allows the system to handle the question correctly.
...considering it basically spam at this point?
It's also technically not spam. It's not advertising anything, it's not a bunch of random letters and symbols whose primary purpose is to suck up bandwidth. They are legitimate questions. In fact, if this user had waited a week between each question, I doubt this would have been brought to meta at all.