note, I'm not an expert, or even any good, but from what little i know:
2. Dont think theres much in the ways of small fights in CoC, if its come to violence shit has already gotten out of hand. I guess something along the lines of Aaron's Super-Professor vs G-man in Bryson Springs would count as a small fight, so 1 on 1 against mundane guys unarmed not looking to outright murder each other is about it, much else and it gets dangerous fast (since on average you only have about 7-13hp per character.)
4. spot hidden, listen, maybe some sneak and hide, library use, psychology and fast talk or persuade (if it fits the character) are pretty helpful
5. Enough so that at least one character is stark raving mad by the end, maybe approaching it by the middle. It maybe should also kinda be pretty tapered, so at the beginning theres not much loss until they really start getting into it and then a spurt in the middle where theres oodles of SAN checks and probably taper off near the end when theyve been desensitized (theyve already seen a bunch of monsters, done stuff they'll probably regret and already have a temporary disorder by then)
6. Violence, knowing too much, seeing shit go down