I can only help with question #3 Taken from
www.sigarms.com
"The sig pro SP 2340 is available in either .357 SIG or .40 S&W. The sig pro features a polymer frame using the latest technologies in synthetic materials manufacturing. The sig pro also features an integral fire control unit for easy conversion from SA/DA to double-action-only, integral accessory rail to mount a tactical light or laser sight, and a unique four-point safety system. The magazine release is reversible for the left thumb to release the magazine."
Since the fire control unit is modular, I would imagine that the Sig Pro will eventually be available in the DAK set-up if it isn't already. Hope that helps.