Don't agree with this.. While sure if you have IPv6 then yeah be nice to do that.. But it sure doesn't have to do anything IPv6..
And while I agree you should do dnssec - again not a requirement.. You do not have to setup dnssec - and people using dnssec will still resolve you. Unless you try setup dnssec and you mess it up.. Then yeah if your dnssec fails you won't resolve.
He is trying to show you that yes it gets complicated very quickly.. But when it comes down to setting up a slave. You tell your master what IP are you slaves, and you setup the zones on your slave and tell them the IP of the master.
But he makes a good point about your PTR.. Can you even set that either of your NSers IPs? That really should be set.. Is where you running pfsense even a static IP?
What are you going to do if someone attacks your dns? What are you going to do if someone tries to use your NSers for a amplification attack and you didn't secure for that? What your using for NS should not be recursive.. An authoritative NS should not do queries for other clients. They only should answer for the domains they are authoritative for..