I'll throw out some ideas to boost knowledge:
Maybe your DM would consider the feat at the bottom of this page:
Infernal Adept featEven a one level dip into Dragonfire Adept wouldn't be bad. Grab the Entangling Exhalation feat as a debuff while you're at it.
There's a feat called Master of Knowledge, +1 to all knowledge checks, but if you are dragonblooded it ends up being more efficient to take the feat Draconic Knowledge (yes, there's a feat with the same name as the invocation) and stack on more "draconic" feats to gain higher bonus to all knowledge checks, along with other cool stuff.
If you a gnome, you can grab the Trivial Knowledge feat from Races of Stone so you can roll twice on all knowledge checks.
Complete Mage has the Otherworldly Whispers warlock invocation to get another +6 to knowledge (arcana, religion, and the planes).
Allies or level dips for skill check boosts (preferably allies):
Bard (inspire competence, + 2)
Marshal (motivate intelligence, + marshal's charisma modifier)
Dragon Shaman (or marshal) (insight aura, +X)
Since E6 caps out at 6th level, you can get your hands on up to 3rd level spells. Check out the spells Wieldskill (+10), Guidance of the Avatar (+20), Divine Insight (+5, +caster level), Lore of the Gods (+5 or +10).
Magic items from the Magic Item Compendium worth checking out: Tome of Worldly Memory (+5, three times per day), Scrolls of Uncertain Provenance (+5 all, with alignment restrictions), Tome of Ancient Lore (+5 arcana and spellcraft, also alignment restrictions).
Unearthed Arcana, spelltouched feats, page 92, "Breadth of Knowledge": all knowledge checks you make are treates as trained checks, even if you don't have any ranks in the specific skill. If you have at least one rank in the specific knowledge skill in question, you gain a +1 bonus on the check.