Brutus goes against Caesar because he fears that Caesar will get too powerful if he becomes king. He felt that if Caesar died rome would be saved.
One the omens that Calphurnia mentions in scene 2 is her dreams. Her nightmares foreshadowed Caesars death. She dreamt of Caesar getting murdered.
Letter of Introduction Format
Write a greeting.
Start with a sentence on why you're writing.
Present the full name of the person you're introducing.
Explain their role and why it is relevant to the reader.
Provide information on how they might work together or be helpful for each other.
Hope this help you!
The last one
All my confidence in that crossing had vanished