Hey, welcome to Empire. First thing’s first, you don’t have to slot neatly into an archetype, or have an archetype at all, but if you take chirurgeon then you can happily call yourself a grimnir, I’d imagine.
Coming as a solo player can be very difficult at Empire. I play a groupless character, but there’s lot of things that people come to Empire to do that I’m not very interested in, so your mileage may vary. It might be a good idea to put feelers out either here or in the appropriate facebook group to see if any groups might accept you as a member before arrival, or make finding a group to join an IC goal for your first event. Otherwise, I think being solo might exacerbate one of the problems of joining Wintermark, that being that it’s the largest nation by far and so getting a slice of the game can be hard.
If you’re open to altering your choice of nation, the Varushkan Warden archetype is all about hunting and warding against monsters, the Marcher Beater archetype similar is about ranging the wilds to keep folk safe (but with less monster hunting), and Dawnish knights are known to hunt out glory in the form of monster slaying (although tend not to have much of a pathfinder flavour, and Dawn is the second-biggest nation and very group-focused from what I can tell). Navarr are known generally for being rangery types who go about with a blade in each hand or a bow slung over them, but I don’t think they have an archetype that evokes the flavour you’re after. If you’re already dead-set on Wintermark, though, pay me no mind.
Also, I don’t take the battlefield myself, but Ambidex and Marksman strikes me as an odd combination, if only because it seems logistically awkward, but I guess ask some soldiers about that one.