Yep, she can testify against him. That should be enough to put some pressure on. She might be precluded from testifying to any marital communications. Different rule.
Yes, but only in court, and only during a proceeding that puts her husband in jeopardy, correct?
They want to nail him for espionage and any number of other items, but the real targets are above him.
The first to squeal gets the deal.