Maybe you could use Custom HTML elements to plant anchor tags throughout the form, and use another one with absolute positioning to provide the navigation.

EDIT: I'm not sure which version you are running, but 10.2 introduced Pagination, which would allow you to break the form into "Pages" that can be navigated in a variety of ways, such as tabs, drowdown menu, or buttons. In your case, tabs sound like they would fit your needs very nicely.