If anything, it made it a bit more frightening... It gave the reader access to his insane mind.
For number 1, your option is correct (B). "Doggedly" is synonymous with "persistent," so "with great determination" matches that.
For number 2, your option is correct (D). "Stoutly" means "strong" and "sturdy," so "solid" would also work.
For number 3, your option is incorrect. The correct answer is B. "Boisterous" and "rowdy" both mean energetic and noisy. Since the children were bouncing off the walls, they were indeed energetic, boisterous, and rowdy.
Answer: It is not. The correct way of saying that is ''We have known each other for just a while.''