Would it have helped him if he had encrypted it, or would he have had to reveal it anyway?

He would have to reveal it, and refusing to decrypt would be a contempt of court charge, or a "jury, presume that everything in this damn document is the worst you can imagine."

This is why politicians don't write things down and can 'never recall'.

With a duress password, it could have allowed him to destroy it, but that itself would be illegal and he'd likely be found in contempt of court and probably with some other charges related to tampering with evidence. But he wouldn't have had to have read it in court. IANAL

Would he have had to provide it if it were locked in a safe?