Yes, I could have said "They drive me crazy." I guess the difference is that "they drive me crazy" is a general statement, and "they are driving me crazy" tells more specifically how I was feeling at the moment when I wrote the post.
And thank you for using real words, capitalization, and punctuation in your post, as well as saying 'Thanks"!
Yes, it's informal, but it's very common -- and, unlike "wanna," I consider it an acceptable ellipsis ("Do you" is "understood" but not stated). I suppose, to be perfectly correct, I should have written "Do you want me to respond to your question?" (or "Would you like me to respond to your question?") but I was aiming for a conversational tone. (I was looking for a tone that said "even though