Leo didn't know what he was going to say because he genuinely wanted to separate from Erin. Aside from that, he didn't need to divorce Erin because it was Jane who managed everything so he could have his faked wedding. However, even though their wedding was manufactured from the very beginning, it doesn't mean that Leo could drive Erin away from him.
What Leo had been thinking was if he wasn't near to Erin, he wouldn't even know what Erin might be planning against his family. That was the reason why he wanted Leah to stay in their mansion first, to make sure that his sons and wife were all...