Step-down Regulator Voltage Drop / Frying
It looks like you misplaced the feedback resistors. They are tapping off   the wrong end of the inductor. 

Making a switched regulator on a breadboard is asking for trouble. If you check the manufacturers demo board layout you see that its nowhere near this type of breadboard layout. With this you will have stray capacitances, messy ground paths to mention some of the problems.