Ohio mass shooter Benjamin Jones spouted white supremacist conspiracy theories and had been admitted to a hospital for mental health evaluations three times in the past two years, a source revealed to The Post. Jones, 20 — who turned a Hi-Point .45-caliber carbine long gun on himself after opening fire at a Walmart in Beavercreek, near Dayton, on Monday, injuring four shoppers — also never attended public school, and hung a Nazi flag on the wall behind his bed, according to the source. “There were warning signs and red flags,” the source told The Post a day after the shooting,...