Dietrich H.

Tori Tori no Mi (or perhaps the Mera Mera no Mi was misclasified and is actually a Zoan), Model: Salamander, Bombardier Bettle, or Red Panda could be 3 variations that might be tied to Mother Flame and need to be awakened prior showing the animal form. If Blackbeard had a tie to Mother Flame, it could further strengthen a Zoan fruit based in Fire. Did Sabo a Smile version of the Mera Mera no Mi or the actual Devil Fruit?

If Blackbeard's plan was to kill both Ace and Whitebeard, then it's possible that he's been chasing his other lesser choices As his consumption of the 2nd fruit may have started a countdown of sorts and ifhe doesn't balance the bit of Mother Flame he has, it will consume him.

The reason Blackbeard can hold more than 1 devil fruit could actually tie back to a devil fruit but not one that he's eaten. It could tie back to the munch munch fruit. We have already seen that King Wapol will munch and combine people. Perhaps Blackbeard was a "failed" attempt for him to combine 3 people. This could have resulted from a deliberate attempt or even accidental attempt. We all know one of his men logs everything he eats to make sure he hasn't forgotten anything. This coujd have resulted from trying to combine 2 people and having forgotten he ate someone in-between or perhaps something. Something like the Mother Flame that he thought was just a bit of fire could add to his bungle in creating Blackbeard and would explain his extra's. The Mother Flame could either keep him awake / energized or a fire not tended could die out or rage out of control either would explain his inability to sleep. And to support this theory you only need to look at Blackbeards flag which represents King Warpol eating 2 people. 2 complete sets of skull and cross bones and an extra skull.