Thank you for your inquiry. You don't say whether your father was in the U.S. Navy Armed Guard although based on his wide-ranging assignments and the fact that you posted your question here suggests he may have been. But no matter, the following suggestion applies equally regardless of the nature of someone's military service.
You should be able to obtain a copy of your father's official military service record. Please see this page from the Armed Guard website that I manage: http://armed-guard.com/searchmil.html. In particular see section A.1. Records of Individuals - U.S. Military. You will have to contact the National Personnel Records Center in St. Louis, MO, a facility operated by the U.S. Archives. Provide as much identifying information as possible about your father. The links on the web page above will take you to the necessary pages of the Records Center web site. His military service record should contain such information as dates of enlistment and discharge, the ships to which he was assigned, applicable dates, training, any decorations or medals earned, injuries or illnesses while in service, etc. There will be a fee for researching, photocopying and mailing the information but the Records Center staff will not begin research without informing you of any charge. Depending upon the size of his file the fee may be considerable but you may find it worth your while whatever the case. There will not be a better source.
The kicker in this suggestion is that due to pandemic considerations a response may be seriously delayed. Even in the best of times a request might not be answered for months. I have heard second-hand that the Records Center is sending back requests due to backlog and suggesting requests be made again at a later date. So be aware of delays and disappointments.
I hope this information is useful.
Your father was a brave man. They all were.
Good luck and best wishes.
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website