WHEN TOM ARNOLD opens the big wooden door of his house in Beverly Hills on a Tuesday in late spring, he’s wearing a blue T-shirt with a Superman “S” logo on it. On the floor behind him is a pink, toddler-size Minnie Mouse car, property of his two-year-old daughter, Quinn. “Hey, buddy,” he says, out of breath from his flight down the stairs, and still sweaty, post-shower, from his morning cardio. He lost 90 pounds five years ago, when his son, Jax, was born, aiming to stick around for the family he’s built with his very patient fourth wife, Ashley. Since then, he’s gained enough back to land at a football-coach burliness — still not bad for a 59-year-old who once blew a $10 million Jenny Craig sponsorship by gaining…
