Two things:

Thing 1: Paul Manafort: Trump ex-aide lied to prosecutors, judge rules (BBC). Manafort is fu-u-%$k-ed.

Thing 2: 18 U.S. Code  875. Interstate communications
(d) Whoever, with intent to extort from any person, firm, association, or corporation, any money or other thing of value, transmits in interstate or foreign commerce any communication containing any threat to injure the property or reputation of the addressee or of another or the reputation of a deceased person or any threat to accuse the addressee or any other person of a crime, shall be fined under this title or imprisoned not more than two years, or both.
"the term extortion means an offense that has as its elements the extraction of anything of value from another person by threatening or placing that person in fear of injury to any person or kidnapping of any person". The important elements are the "threat" and "thing of value". Not pursuing a lawsuit or other action is, by definition, "of value" to AMI. The standard, as we just saw in the Manafort case, for a violating of an agreement not to prosecute is lower than criminal conviction. AMI screwed the pooch.