So I'm playing a stealthy sniper type fellow at the moment, but the strength requirement is 6 for the hunting rifle and my strength is 5. How much/in what ways do strength requirements affect guns? I've been using the hunting rifle for maybe 2 hours now but not a lot of the time was spent in combat.

It basically means that if you don't meet that requirement, you wont be able to shoot as well with it. The accuracy with that gun will be lower than how it usually is and you will also have increased sway while aiming. Meeting that requirement improves your accuracy and lessens the sway to default.

Your aiming suffers, you wobble like you have a crippled arm. Get the Weapon Handling perk that lowers the STR Req. by 2.

Can most of the sway be conteracted by standing still and crouching? thats how most of my kills are made, though I don't know how the game calculates accuracy exactly

EDIT: I've also used the gun on a seperate character with 6 strenght and didn't notice any immediate differences from using it with 5, but I may notice more later on. However, I do know that it's not as bad as a crippled arm, I can't hit anything with a crippled arm unless I'm using a pistol though I can make 3/5 shots from a medium distance with the rifle at the moment, but that may improve once I find a scope for it.

Sorta kinda

It can, but not as much as it would be by default.