Question about the note...Why leave a note? He didn't take the body with him.
BUT, today he said it was an accident. Now, leaving the note makes sense. It becomes proof it was an accident.
It's him. Read the letter. You can see the "character" of the writer and it's a match.
Remember, his resume listed hobbies: Writing, ACTING. What we saw on TV was the "actor". You could almost see him "enter the role" just before he spoke each time.
Patsy Ramsey's hobbies were also acting and writing.