Informing Israel of terrorist attacks planned against her did the US "incalculable harm"? I'd be interested to know the exact nature of that harm.
The exact nature of the harm is irrelevant (even though American agents in the Soviet Union died because of Pollard's actions). When you get a security clearance you swear not to disclose the secured information to unauthorized persons. The Israeli agents he gave the info to were not authorized and he was not in a position to freelance the decision.
Further it is common for "false-flag" operations to be used to convince an agent that they are working for one country and are actually working for another.