1. This is terminology from a holdover, and is just dice from having applicable equipment as a condition.
2. Same again; there are just two tiers, the granular score and the have-it-or-not bit. The clearest terminology, in tests, has turned out to be the D&Dism of "ability score" and "proficiency", which annoys me, but clear is clear.
3. Fair, that. I've had readers go both ways on that, (your way and the reverse, where envisioning the general rules is hard without knowing character bits).
4. Not *exactly,* but if you click over to my storefront, there are a few free games in various states that use forms of the general engine, some of which demand a lot less 'co-designer' work (Infected is pretty close to 'just make characters and go').