I would raise all meritorious grounds for dismissal in one motion. If judge orders you to answer I would answer.
There is no substitute for the professional advice of an attorney who knows your case and represents you. My post is not, and may not be relied on as, legal advice and does not create an attorney-client relationship. Best wishes for a just and expeditious resolution.
A motion to dismiss usually arises from whatever defects are apparent from the four corners of the complaint and its exhibits. Lack of Standing. Statute of Limitations. Failure to attach the agreement. Lack of subject matter jurisdiction in the chosen court. There are many, many other potential reasons a court might be required to (or have discretion to) dismiss a particular case.
Use all of 'em you have, or lose 'em.