I'd agree that something sounds off about 2014 and 2014 filings. Are you saying that 2013 has not been filed yet? If you had a bad SSN, the return would have been rejected by efiling, but once the correct number was entered that should have been cleared up. If you need to do any amendment on 2013 for any reason, the statute of limitations is 3 years from the original due date of the return so you have until April of 2017 to get it figured out and get any refunds due to you.
Going back to a sole proprietorship could be an option, but you would need to revoke your S-Election and file a new 8832 to elect to be treated as a disregarded entity. You would need to do this before March 15th of this year for it to be effective for 2016. You will still be an S-Corp for 2015.
POA, at least for the IRS, is only for specific forms and specific years. I personally wouldn't worry about revoking it, but that is your call. Why was POA given in the first place?