I don't know, I just don't see it being the Batarians. They're like humans, but farther back, so why wouldn't it just have been humans from the start.
Re the quote - Yeah, it probably was just lazy writing tbh - they were rushing to get the EC out, and being realistic, had they name-dropped an arbitrarily named new alien race, then that would just lead to even more questions, so I'm willing to forgive them for that omission. In the grand scheme of things, that was a very minor gripe compared with some of the other complaints.
Re the Crucible, I thought it would somehow involve the relays, that much seemed fairly obvious I thought. I didn't foresee the Starbrat though, I doubt anyone in their right mind did.
Destroy - the only choice really. It's what I went to the Citadel to do, kill the Reapers. Not to become TIM/Catalyst 2.0, and not to create the master-race through genetically raping the galaxy via space magic. Destroy ends the Reapers' billion-year cycle of bullsh1t. Sure, there are casualties, but as you said, EDI and the Geth knew the score, and willingly signed on. It was a sad loss, but an acceptable one. Compared to doing an about-face and suddenly deciding that TIM and Saren had been right all along, or from changing the nature of all life in the galaxy (and effectively giving the Starbrat exactly what it wants), then the loss of both EDI and the Geth, is a small price to pay.