Regarding finishing highschool via the military, can‘t be done... once you‘re trained, you can probably finish the credit through night school, if it‘s only one credit... on the other hand, if you have the option right now, you‘re just as well to go back... if you‘re only 17, don‘t feel pressed to "decide where you‘re going in life" right away if you don‘t have to make that decision right away... I‘m 19, I still don‘t know what I‘m doing, I‘ve got a friend who‘s 29, he‘s been through at least a dozen careers, he doesn‘t know what he‘s doing, and I know retirees who still don‘t know what they want to be when the grow up.
On the other hand, without a high-school dimploma, you‘re severely limiting yourself.