The smallest inside diameter of the chamber is at the very top and is 2.66″ or 67.6mm.
The thickness of the steel is just under 1mm.
Yes. The cafe has a silicone o-ring like a traditional moka pot.
Not yet, however I am working with the factory to evaluate different colors for the top surface. Making this option available will depend on whether the color/finish becomes damaged or discolored by heat.
At air temp of 79F (26C) it takes 2 minutes to bring 2oz (56g) of wood (loaded combustion chamber) to a sustained burn, then just over 3 minutes to bring 8oz (227g) of water to a boil. The 2oz of wood burned down at 8-9 minutes total. Reloading the chamber can indefinitely extend the burn.