You could use a TransformEventValues to replace every instance of !BPM with something like this:
{!BPM * (1 + (!Jitter * 1 s random))}
and similarly replace !DutyCycle with
{!DutyCycle * (1 + (!Jitter * 1 s random))}
The TransformEventValues would go to the right of the Chopper and transform all Sounds to its left in the signal flow.