I see a couple of ways to get this information but an underlying question is this: What port will you include in the pool name if the user enters different port numbers on the members? In other words, what if one pool member is at port 80 but another is at port 8080? (This is allowed...) If all members must be on the same port, why not move the port setting completely out of the table into a separate string field that is its own variable?
To access values in a table, you have to loop through the table. I'm guessing there is already code in the Implementation Section to extract the selected nodes' IP addresses and user-specified ports, and build the member list that will be used on the tmsh create command for the pool. After the loop completes, you could extract the port specified on the last member to use in the pool name. Something like this perhaps:
set MemberList ""
foreach TableRow $::pool__members {
array set ThisRow [lindex $TableRow 0]
lappend MemberList "$ThisRow(address):$ThisRow(port)"
}
tmsh::create "/ltm pool ${location}_${FQDN}_${ThisRow(port)}_pl members replace-all-with { $MemberList } ..."
(I'm assuming $location and $FQDN have been set previously.)