Can you explain what is the objective of the page spread setting. It seems only to add extra space around the page viewport.
I was trying to have put an illustration that spreads into two pages.
The page spread was introduced to enable you to layout images and other objects outside the viewport, and eventually bring them in via the actions (with an animation or a move, for instance). You can set this both at a project level: under General Settings the Page Spread property is set by default to auto - you will have automatically a Page Spread double the size of the viewport. Otherwise you can customize the Page Spread value to your needs; you can also set this value at a page level: go to the Page Inspector, under the Workspace tab you will find the Page Spread property.
In order to have two spreads in a unique view, you need to set the Single Page option to false, you will find this under General Settings -> Appearance and Behavior. In this way you will have your output (on iBooks, for example) with your even pages on the left and odd pages on the left - for example page 2 - 3 will stand one next to the other.
You can add page navigation by placing two graphic images representing the arrows and add a browsing action on Touch such as "Go to next page" or "Go to previous page" to each one.
The 2 arrows will be visible on each page.
Placing the arrows on the "Overlay layer " will make them visible on each single page.