I don’t think anyone really knows how Google generates the search entry. My only comments is that the additional post titles are not included in any meta information on the generated page, but those extra titles are currently the posts listed on your home page. This is not likely a coincidence. Nothing theme related unless the Schema entries included by Weaver Xtreme in the output HTML help trigger information Google gathers. That is the point of that feature, and there is an option to disable it if that might change the indexing Google generates.