You should put, rather than "named_enable",
in
/etc/rc.conf (no quotes needed).
I would remove the reference to "named_program", I'm not sure that it's relevant.
You can set named_flags how you want, but to run it chrooted take a look at the comments in
/etc/defaults/rc.conf,
Code:
# To run the named(8) DNS server as an unprivileged user under a
# chroot(2) cage, uncomment the following after migrating the contents
# of /etc/namedb to /var/chroot/named/etc/namedb
#
#named_chrootdir="/var/chroot/named"
The last uncommented line should of course be placed in
/etc/rc.conf .