i wouldnt use any sealant. these fittings are designed to not need sealant. your fuel system is low pressure so you should be ok. if you use the ferrule just make sure the surface of the tube is in good condition. no rust or pitting and you should be fine.
I am not really sure. It is mounted after a Holley Blue pump and before my regulator. For the pump, JEGS says... So if this is true, it should be fluctuating between 10-15 psi depending on need at the time.