HUNTING VALLEY, Ohio — Saul Malek tours the country as a cautionary tale for kids. In a previous era, he might have been a reformed drug addict or drunken driver. But Malek, 28, showed up at an all-boys private school in Cleveland last month as a human billboard warning of the newest vice tempting America’s youth: online gambling. Malek took the stage at University School at 8 a.m. for a day of sessions on the dangers of technology that has turned the world into an always-on casino. “So who are my sports fans in the room?” he asked an audience of teenagers, each wearing a dark blazer and button-down shirt. Hands shot up across the auditorium. Malek told the high schoolers how a single $10 bet on a baseball game in his teens spiraled into a destructive habit that left him $25,000 in debt and contemplating suicide by the time he was 21. “You don’t even realize that what you’re doing is harming you as it’s happening,” he told the boys, a message he’d later repeat to the school’s seventh and eighth graders.…