I have been spinning on this for many several hours now and am reaching out for help. Thank you guys!
Here is /boot/grub/grub.cfg http://termbin.com/edvw
Here is /boot/grub/custom.cfg http://termbin.com/90wi
Notice towards the EOF in in grub.cfg is #410 section .
If the #410 section is included, then my grub will have TWO, identical 'funtoo 410' entries listed on my grub menu. (one from grub.cfg and one from custom.cfg)
If the #410 section is omitted, then I crash to grub rescue command prompt. I was expecting to still see one SINGLE entry from custom.cfg, but it never gets sourced in this situation!
custom.cfg appears to only get sourced if I have one menuentry stanza in grub.cfg !
My other computer has no menuentry stanzas in grub.cfg, only in custom.cfg and it displays all the menu entries in grub perfectly.