http://www.uscg.mil/nmc/professional_qualifications/pdfs/crediting_military_ss.pdf
http://www.uscg.mil/nmc/professional_qualifications/pdfs/enlisted_personnel.pdf
E-4 and above holding a Dwo counts for mate time. So if you have the sea time which I’m sure you do then you can take the classes then submit for approval to test for 1600 master and 3rd mate. I don’t think the 210s are big enough for the 3rd mate but it’s worth a shot. Just so you know holding the masters lic won’t land you a masters job. You will still have to start closer to the bottom as an AB or training mate (if your lucky) depending on what sector of the industry you go into. So plan on the possibility of being a non rate making chief pay to start out. You did mention tugs and there you can def plan on ridding as a hand until you learn the ropes, it will also require that you get a TOAR completed before you can legally ride as a mate. You can accomplish that through diamond marine services in NY or by doing it on a tug with a qualified assessor. As far as transition from active to civilian I didn’t have any problems but its due to the fact that I was realistic about not starting at the top. Your transition will be easier than mine as far as the licensing process goes though. I was a heavy wx guy and 47s don’t weigh to much so I had to put in lots of deck hand time on heavy boats before I could upgrade to a bigger license. You however are in a good spot and as stated above should be able to test for 1600 master right out of the gate. To sum it up take the classes get lapware study your as off!! (the exams are not easy) take the test and then start knocking on doors and getting connected with folks.