Just my thoughts, please dont take it for facts!
Correct me if Im wrong
Well, for nr 8, you can just think for your self, big airplanes - high speed planes, right? (Swept back wings, boundary layer fence etc).
Now, if you look at Gust Load Factor table, you will find out, heavy airplanes can take less gust load.
As well, IF you should encounter windshear/gust, its much harder to recover (swept back wings, wing tip stall first, pitch up moment etc) and you need time to get those big engines spinning, while response from prop. is immediate.
So, combination of those 3, plus more strict regulation for Jet Transport for safety margin, gives you higher descend speed.