Heard back from the company today - my seniority date will be my original hire date, though the time I spent furloughed before requesting military leave won't count for longevity (lose a couple years there, but oh well, it's still a ton more than anywhere else).
Also did a lot of digging on a law review site run by the "reserve officers association" where one of the original architects of the law posts opinions - sounds like I legally snuck in under the wire as far as USERRA is concerned given my original 7 year commissioning commitment for student loan forgiveness and associated pro dev course ADSOs, but my 5 year elective time away is now spent. Either way company is honoring it so I just need to do the 1 weekend a month and 2 weeks a year thing from here on out or be involuntarily called to active duty.
They also are suggesting 6 months back on the line and then upgrade...which sounds perfect to me.
I'm waiting for my car to get totaled or DT to declare war on China or something. Keep wanting to pinch myself.