Yes, the PO Box address was the correct place to send your RFE response. USCIS does not always update the online case status system automatically so it will likely be within the next week or two that you see a change of status noting that your RFE Response was received.
This answer is for informational purposes and does not take the place of a consultation with an experienced immigration attorney. This answer does not create an attorney-client relationship.
1. Yes, that was OK, you did all right.
2. I wouldn't "hold my breath" on this one, as the USCIS online status site is notorious for not being updated on "real time". I would say a month or even more.
Kindly be advised that the answer above is only general in nature cannot be construed as legal advice, given that not enough facts are known. It is your responsibility to retain a lawyer to analyze the facts specific to your particular situation in order to give you specific advice. Specific answers will require cognizance of all pertinent facts about your case. Any answers offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship.
You have to mail the information requested to the address they ask o mail it to. Once they receive the information and process it, the status will be changed online if changed in their system.
This answer is not intended to replace a consultation with an attorney and does not create an attorney-client relationship. Please do not contact me expecting additional free advice. If you contact me privately, I will email you an invoice for a consultation and will advise you only after the invoice is paid. Thank you.