Rogerio,
The F and R are front and rear. One is the wafer closest to the shaft behind the metal wafer with the collar for the shaft. Position 1 is usually the fully CCW (anticlockwise) rotation position.
If you find the diodes leaky to the gate(s) of the dual fet, 1N4937 will work. These have very low reverse leakage and are the best ones for the d-c restorer circuits because of the low leakage, low capacitance, very fast trr and have a 600V rating vs. the 200V used in the d-c restorer circuits. Going higher in PIV on a diode is fine and sometimes advised (d-c restorer circuits is one example).
Mark
