NLB allows admins to set up a node to handle 100% of the load for a particular port. If that node fails, will no other nodes handle the request because of the port rule?
Not necessarily - as long as at least 1 other node in the cluster has a weight greater than 0, that node can take on all traffic for the cluster. If all your nodes have a weight of 0, then traffic for your cluster will indeed stop. A weight of 0 essentially stops that node from taking on any traffic, even in the event of other nodes failing.
The reason this is possible is because the weight does not equal the actual percentage of traffic that node will take. You can set all your nodes to be a weight of 100 if you wish. The actual calculation that determines how much weight a node will take is:
So in a 2 node cluster setup as node1: 100 and node2: 0, general operation will put all traffic to node1, and the failure of node1 will cause a failure of the cluster.
In a 2 node cluster setup as node1: 100 and node2: 50, the general operation will put 66% of the traffic to node1 and 33% to node2. In the event of a failure of node1, 100% of traffic will go to node2, and vice-versa if node2 fails.
Sounds like you want Single Host filtering node. This puts 100% traffic on your chosen server and will failover to the other(s) if it goes down.