Welcome to the forums, CarsonC1974!

I couldn't find duty cycle specs for the 256D version. For the non-digital version, duty cycle is 35%. The 250EX duty cycle is 60%.

Speaking to your other questions, a water cooled torch is required above 200 amps, so to get the most out of the machine you'll need a cooler.

Call and speak to Mark (screen name Performance on this forum)- he can quote attractive prices for you. (He's been under the weather recently- you may need to leave a message.)

DaveO