Sorry, but the Yomi Yomi no Mi and the Yami Yami no Mi are NOT the same thing. Blackbeard has power over gravity, which really makes me wonder why his fruit is the Darkness fruit. But of course, if we were going strictly by names, Brooke's Yomi Yomi no Mi would give him the entire power of Hell, so… (Yomi is the name of the underworld in Japanese)
Anyway, I'm pretty sure it's the Kage Kage no Mi. Besides, there's no four letter word for Mirror in Japanese. Mira- is the only thing close, and that's used as a prefix, I think.
Although, that made me think... how about a zou zou no mi? (Image Image Fruit)? That is, he makes a photo realistic image of the person, a "negative" of the person, so to speak, aka... a shadow? Then, if the person's negative is gone, they become "Exposed" to the sunlight, and ruined, like a normal picture is to overexposure.
Get it?
Oh, and we saw Dorry and Broggy's old ship in the flashback. It wasn't as big and looked completely different. Besides, Moria is of Saul's Clan (He's from West Blue), which makes me wonder if Saul knew Moria.