The procurement notices for solicitations site keeps an archive of recent notices.

Agencies are encouraged to post the RFI results summary on their departmental website.  SPO does not have a site for posting RFI summaries.

Yes, accept it.  Unlike the RFP process, the RFI is not a formal process.  Although a due date for RFI responses is set, it doesn’t prohibit you from accepting responses received after the due date.

Unless the information provided is confidential or proprietary, the responses are public record.