No it wont include IAP by third party as those apps still come from the App Store.Yes on the first sale to consumer. This we agree. But it makes total sense if you recognize that the apple AppStore is tangible separated from the iOS device consumers use.
Not at all, this must also include IAP by third party solutions that developers chose to use instead of apples IAP solution. Now if consumers use apples IAP button then apple obviously get a cut of that specific sale.
Those apps will get a discount to account for a third party doing the payment processing. Apple are still listing the app on the App Store.
Only apps acquired outside of the apple App Store will be exempt from Apples commission.