There needs to be more facts to answer your question. With the information provided thus far, the Plaintiff would only need to serve its answer to your amended affirmative defenses by US Mail to you and provide a copy to the clerk of court. Nevertheless, affirmative defenses do not need specific responses. They are deemed denied generally is no specific response is filed. Regarding your other question, even if you filed a motion to strike and your motion is based upon defective service, because it appears the case has been ongoing, and unless you showed prejudice, judges oftentimes will deny those types of motions on the basis that the underlying policy in cases is that they are decided on their merits, not technical defects. Again, each case is different, but I would definitely retain an attorney in your case.