I suggest to open a TAC case to solve your problem as fast as possible.
This forum consist of a bunch of volunteers and some Check Point employees, there is no SLA here.
To your question:
You can simple copy all the files from the postfix queue directories (defferred, bounced etc.) to the other cluster node.
And then did an " /opt/postfix/usr/sbin/postqueue -c /opt/postfix/etc/postfix/ -f", which delivers all your messages.
Your shown message "postqueue: warning: Mail system is down " shows that the MTA/postfix is not running. You have to
check why. Without this running you can't send any of your messages.
With "/opt/postfix/usr/sbin/postfix -c /opt/postfix/etc/postfix reload" you can try to restart postfix. If it not starting check
ATRG: Mail Transfer Agent (MTA) for troubleshooting.
Your output shows only one message, which is not delivered. Maybee this message is really important for you.