I always run a low fuel pressure switch. That's up to you. If you do just be sure to install it on the high pressure side of the regulator. The pressure deviates too much on the low side and would just be a headache as the switch will blip when the fuel pressure has the slightest stumble. The real protection is a fuel pump taking an unexpected dive.

The retard appears to be hooked only to the first stage of nitrous. It needs to be at least a two stage retard and be hooked to both stages. Depending on the type of retard as in how it needs to be wired. Digital retard work different.