A deranged, 300-pound man took his 2-month-old son hostage and torched the family Christmas tree during a wild standoff with cops, police said yesterday.

Tredon Mann suffered a broken arm and a bad cut. His dad, Trevor, 26, was charged with felony assault, assaulting a cop and arson. Trevor was taken to Kings County Hospital’s psych ward.

An off-duty cop saw Mann’s Nissan hit a van in East Flatbush just before midnight Friday night. Mann ran five blocks home as the cop gave chase, setting up the rest.