Okha have less then 100km range,V1 - 300km.And could be used from bombers.
Which mean,that Japan could send bombers which would release V1 300km from targets,so american fighters from carriers could not schoot down those bombers.
If they have enough of them,they could gradually sink enough american ships to stop onvasion of Okinawa.
About sarin - that is why it must be used on England cities.And lesser lethality is even better - dead cyvilians could be just buried,when injured must be healed.
If germans fired enough V2 with sarin on London,british health system would fall.
Aside from that - Happy Easter !