Thanks for that awesome explanation!
Yes indeed, with a process server knocking on the door, you absolutely did the right thing by filing a timely answer. I am relieved to hear that you did so. The absence of a case number is not out of the ordinary...sometimes that is not assigned or stamped on the documents until later. In any event, the most crucial thing is that you are absolutely right...you did need to answer and failing to do so would have risked the entry of a default judgment against you.
Everything else you mention makes sense as well and raises no eyebrows so to speak...i.e. the way discovery is going, the standard "We are a debt collector" disclaimer language, etc.
Now, the heart of your follow-up is the second to last paragraph (above) where you ask five separate but related questions. Actually, this takes us right back to your very first comments. In other words, there is nothing you must do at this juncture. You were served, you timely answered, both sides have exchanged discovery back and forth. So, there are a couple of ways to go here. You can obtain the case number from the clerk (either in person, telephone call, or in many cases nowadays online)...that should be a simple matter. That would be the first step. Thereafter, you could focus on discovery in seeking to compel better answers from them...along the lines of a motion to compel based on their lack of responsiveness. However, I would go right to your very first mention and file a "Motion to Dismiss with Prejudice". That would be dispositive...it could summarily dispose of the whole case and make it go away. I have been on both sides of such cases, and frankly I would go ahead and just do so without delay. Call their bluff...if they have some better proof, this will make them cough it up or risk the dismissal of their litigation.
And, to address your final paragraph, you are most kind. I deeply appreciate your confidence and would be honored to assist anyone you might refer. To reach me directly, all one would need to do is type a question in the "Ask Your Question" text box on my Profile Page.
I hope that all makes sense...you have a great understanding of the process. I would not recommend it to just anyone, but I have no doubt you will do just fine with this on your own, at least for the time being. Should things unexpectedly somehow turn complicated, you could always seek additional help at that point. For now, however, I would say just go forward with your motion as discussed and see what happens.
Take care and thanks again for choosing JustAnswer®!