Yes, the 2/3 means the front shifter will work with either a double or triple crank. The shifter will have four clicks that give four front derailleur positions, one is a trim. For a triple crank you use them all. For use with a double you adjust the front derailleur's low limit screw to keep it from moving too far inward and set the shift cable tension to use the outer three fd positions. (small ring, trim, big ring)

The reason for setting the double that way is that if you use the non-functional click, the cable merely goes slack. If you set the shifter to use the inner three positions and try to shift into the fourth non-available position you can break something.

Any flat bar brake levers designed to use with cantilever or caliper brakes will work with your Ultegra brakes. You cannot use levers designed for V-brakes.