Bunsen Burner Control Valve Regulator

What is the maximum line pressure you can get with this regulator?

Brass barb is 1/4" (6.35 mm). eisco burner inlet is 8mm (0.315 mm). eisco hoses fit 8-10 mm. do i need an adaptor for 6mm to 8mm? another barb?

Does this item work with standar 57 gallon propane tanks

What is the threading on the brass barb? Are larger barbs (8mm / 0.315" for example) available?