A) claiming the brain "is not a formal logic system" either makes the brain weaker, or says that the Church-Turing hypothesis isn't true. It takes a bit more than hand-waiving to make that claim.
B1) C. Elegans has evolved to understand its environment.
Sure, we don't understand (can't predict) everything about our environment, but the level of complexity we can understand - Saturn V rocket for example - is pretty astounding. If you look at the brain as a bunch of interacting subsystems, then the level of complexity really doesn't appear that great. I think historically people have overestimated the theoretical complexity of the brain for a variety of reasons.
B1) C. Elegans has evolved to understand its environment.
B2) We don't understand our environment.