Hi,
the node command can be applied only once in the context of the connection and event.
The assigned port number will be used for the particular connection only.
That´s why I would recommend to use a decission matrix first (whatever your criteria is to pick a specific destination port [poolmember]) and set i.e. the $port variable.
$port will be used as follows:
node [LB::server addr] $port
Due to setting your poolmembers to port 0, the initial server port will be 0 as well.
That´s why your syntax will not have the expected result.
In case you can provide a more specific description about pool member selection in your current deployment I´m happy to have a look at it after I´m done with my customers appointment in appr. 10 hours.