Hillary Clinton has a “Jekyll and Hyde” personality that left White House staffers scared stiff of her explosive — and even physical — outbursts, an ex-Secret Service officer claims in a scathing new tell-all. Gary Byrne, who was posted outside the Oval Office when Bill Clinton was president, portrays Hillary as too “erratic, uncontrollable and occasionally violent” to become leader of the free world, according to advance promotional materials exclusively obtained by Page Six. The allegations from Byrne, a 29-year veteran of the military and federal law enforcement, threaten to derail her campaign days before she is expected to clinch...