In a setting where people spend a lot of time in the wilderness, either on their own or with small groups, it's reasonable to expect that they will have some ability to handle injuries. One or two ranks of a medical skill does not make a doctor, but it might be enough to stop the bleeding so you don't die before getting back to a healer. One or two ranks is more like you have seen someone do it and can give it a shot in an emergency. (My character once stumbled across the dead and dying losers of a battle. By the time he successfully stabilized one of them, he had failed on another ten. This is not a significant level of ability.) One or two ranks, for treating immediate trauma, doesn't represent the level of training where you need any real theory of how medicine or the body works. It's just basics like how to bandage a wound. The only medical theory here is that blood is supposed to stay in the body, and it's usually bad when it comes out. People generally understand that. Details can be left to advanced practitioners.
Herbalism is ok to fill that role, but only if you expect that people in such situations will routinely carry suitable herbs. Once the bleeding begins, it's way too late to search for herbs. Herbalism also does not solve some problems. You can treat someone so their bones will heal twice as fast, but you still need to splint it, maybe put it in a sling. (Properly setting it could be done on the spot, but probably it can wait until you get them back to someone with more medical training, if you are days out and not weeks.) Herbalism won't help you there.
Magic can also fill that role, but only if every hunting party will have a caster with the necessary spells; that's assuming extremely common magic. Definitely setting dependent. I would encourage people to adjust background skill ranks according to their setting.
Characters from highland, harsh, wastes, sylvan, etc environments are likely to spend a fair amount of time in the wild. I wouldn't expect a typical urban character to have much need.
As for throwing knives, I think the biggest difference I have noticed is in the grip and the guard. You can throw just about anything but it's not unreasonable to put a penalty on throwing a knife designed for melee, or on wielding a knife meant for throwing, or expecting to pay a little more for a knife that has been really well designed and will serve for both. Not a necessary detail though.
