Well it’s one of those cases when two wrongs don’t make it right in the eyes of the law. Threats to expose someone aren’t blackmailing. What makes it blackmailing is involving money. He did commit a crime so it would be fine to threaten to reveal perjury. Like if you said “I am hiring a lawyer and I am going to expose you and” or “if you don’t reveal your lies to the judge I’d know you are a jerk” it wouldn’t be blackmailing. Saying you’ll keep it quiet if he pays you, makes it blackmailing.

Just go through legal channels. But now he again has upper hand because he now has your texts. Anyways you can’t win with him trying to beat him at his game. Go strictly through the lawyers/courts etc