Mary Jo Eustace says she had no idea her actor-hubby, Dean McDermott, was dumping her for Tori Spelling - until we broke the news. The Canadian mom tells People.com: “My birthday weekend last year, I came home and somebody called me and said there was going to be something in Page Six . . . So it just kind of exploded.” Eustace, 45, who lives with her kids, Jack, 8, and Lola, 2, adds she’s now shopping a “comedy script ...