Great write up mate.
I've not long had my 100KS and I can echo nearly everything you've said.
It's a great gun, your spot on I get 4 mags from mine from a charge and it's well in the yellow on the gauge.
I'm not sure what you mean by movement between the action and the woodwork ?
Is it up and down or forward and backward?
That sounds bad to me have you checked the screws are tight?
The action is held pretty well in the stock on the 100 I'm surprised at your findings