2. "doubtful"
3. "I am really doubtful about his sadness" ? "I am skeptical about his sadness"?
4. "?" ? "I am skeptical about whether he is genuinely sad, as there might be a key regret that he is hiding or faking his emotions."
5. "I am skeptical it" ? "I am skeptical if he will show up on time"?
6. ?"?" ?