what is the hull of the ISS made of and how thick is it?

Answer 1

The blanket is "up to" 10 cm thick (see ref). Parts of the station that are in the orbital shadow (the trailing side) of the station will tend to have less protection (my speculation). The windows are up to 4 sheets of material each up to 1.25" thick. (see image http://www.spaceandtech.com/spacedata/platforms/worf-window-schematic.gif)

The pressure shell stands off 4" from a 1.27mm sheet of aluminum around it. Micro-meteroids that get through the blankets impact this shell and turn into a debris cloud of tiny tiny bits spreading out the impact on the pressure shell.

The third reference describes this and lists variable probability of pressure shell penetration for the US vs. Russian modules, implying the pressure shell beneath has different thicknesses for different modules.

The ESA module has a pressure shell thickness of 4-7mm (1/6" to 1/4") Presumably the other modules are of similiar thickness.

Answer 2

Aluminum covered by a debris shield blanket made of a material similar to that used in bulletproof vests on Earth. I don't know how thick.