Network Interface setup concern

I am checking on my network interface configuration for my net-net 3820, and have currently 2 concerns i'm not quite clear on.

 

Concern #1 (network interface subports):

Documentation states that default sub port (subport 0) is used when no VLANs / virtual interface destinction is needed.  it also says you can have up to 4095 total, but i'm not quite clear on whether you should skip using subport 0 if you are trying to use VLANs. 

 

My scenario:  I want 4 logical peer networks, with a realm for each (for simplicity).  Currently i have them as subports 0,1,2,3 (again for simplicity).  I'm having trouble getting traffic through my SBC and suspect it has to do with the network interfaces, and i'm wondering if i'm assigning subports improperly.