When did John Proctor realize he was facing his own demise?

Proctor's tragic flaw was his pride, and his pride was the thing that led to his demise. He was unwilling to confess to his own mistakes and allowed things to go too far before finally realizing that he had to put the welfare of others first. I believe he was completely unaware of his ultimate fate until Elizabeth's arrest. After that, he put himself on the line, even knowing his revelations would redeem no one. Note, Proctor was also intent upon regaining his good name.