You never know. Is it possible to send in the contract you signed with the bank when he added you? I would send that in as we'll as the letter and the bank statements. I wouldn't redact them...you don't want to risk raising suspicion, especially considering that they have already issued an RFE. Rarely do they issue second RFEs for any further doubts that may arise.
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I like your first idea of the bank statements with the explanation letter on top. I would not doctor any of the documents, that may raise red flags
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The RFE response should not be limited to the bank statements. Therefore the bank statements are of some consequence but there are other vehicles to prove you are in a bona fide relationship. Best bet is to retain counsel and widen the scope of your response.