The spider eater guy part was the most interesting one of Overture, of course.
The spider eater said that he adventured deeper into the mine. Maby he was bitten by Wilbur and got infected. And that's why he cut off hes tongue?
Also, it could be possible that he saw Red, got scared and ran away. Like he said, hes leg had fracture.
Last time when I checked, Red wasn't the best looking guy of the year...
Frictional Games weren't probably thinking so much about these little things. They just focused on the main story. So, the story may have some flaws. But, these little details makes the game more interesting.