What driver are you referring to?
Regarding the 3D Warehouse and accessing it with SU2016, it has been explained multiple times that since Microsoft has discontinued support for Internet Explorer and there are security issues with IE, SketchUp had to make changes. It’s not the fault of SketchUp or Trimble that Microsoft has decided to discontinue supporting IE.
Sketchucation is an entirely independent entity from the 3D Warehouse and Extension Warehouse.
Yes. You can go through your internet browser to Sketchucation and download extensions which you can then install. In the same way, you can go to the Extension Warehouse in your internet and download extensions from there and install them the same way. As for components from the 3D Warehouse, you can access them through your internet browser, too.
Who is “fredo7”? I know of Fredo6. His extensions are all hosted at Sketchucation. None of his extensions are hosted in the 3D Warehouse.
Fredo6 doesn’t have an stl exporter. Maybe fredo7 does but I’ve never seen any of his extensions. You can still get the .stl exported from the Extension Warehouse and install it in SketchUp 2016 if you want it.