Number 3 seems to be overlooked a lot and it's sad how many "gaming" laptops with top of the line cards have low-res screens. You definitely want a 1080p or 1200p screen at 17".
See I think resolution and screen size are pure preference. Particularly I'm not convinced for the outright
need to have 1080p when 720p (or rather 768p) is just as good. Sure, 12" would be too small for gaming and you'd end up straining your eyes, but there's nothing wrong with 15" screens.
Even when I had a desktop I never really went above a standard 1280x1028 resolution, hell sometimes you still end up needing to lower the resolution to those "sub HD" values to get better performance.