0.68uF is a small value capacitor for usage on AC motor. You have to stick with this one as capacitance and voltage is determined by the physical motor. One can't reduce either the value or the voltage of the capacitor.I meant to ask you why does the motor use such a large capacitor? It is rated .68uF @ 400v. Is there another value I could use to save on space and cost?
After getting more information from your various attempts in building the circuit, I have re-examined the circuit design but see no other possible problem leading to component failure. It would be beneficial to use a lower voltage of 6V or 9V but even at 15V, the circuit should not get damaged.
Let's wait until you have got the proper 2N7000 and fitted them to see if there are more problems. It could help if you can connect "LED with series resistor(2KΩ)" across each relay coil temporarily to see how the relay operates. Do not connect the motor at first before you check that the circuit function is correct. A malfunction circuit would attempt to change the direction of the motor before switching off the power first and this could lead to the damage of various component.
If the circuit functions OK without the motor but fails soon after connecting the motor then there would be a different approach to correct the problem.