Yes. Bring more docs. If they scheduled an interview, it means USCIS wasn't impressed by the amount of evidence you provided.
I-751 interviews happen rarely. It's not something that you should anticipate. Interviews happen in around 10% of cases.
Attorney answers to questions are for general purposes only and do not establish an attorney-client relationship. Please consult with an immigration attorney to get complete answers to your legal questions.
You should absolutely bring more documents to the interview. The focus is usually on your joint life together - financial, social, etc. You will want to focus on the joint documents. I recommend that you go see an immigration attorney for a consultation before your interview so you know what to expect.
Viera Buzgova (512) 476-7163. The information above is general in nature and does not constitute legal advice. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. You should retain an attorney to review all the facts specific to your case in order to receive advice specific to your case.