Make Multiple layers feel like one time line

I'm working on a project right now with extremely long slides, 3 to 5 minute range. To prevent the slide from being boring we're constantly fading in images and bullets to fill the screen, then fading them out to make room for more bullets and images to illustrate the next section of audio. As you can imagine syncing these slides, and making edits later on, is a bit of a nightmare. The timelines are incredibly long and tall with rows of elements.

Ideally, I would like to break the content up into multiple slides, but the client wants the content to only be one slide in the menu. They don't want part 2, part3, etc. And they don't want Slides hidden from the menu. 

I thought about breaking the various stages of the slide into different layers, the next one auto opening when the previous layer ends. But then you can't rewind to the previous stages with the playbar.

Is there any way to break up the stages of layout across multiple slides or layers, but make it feel and act exactly like one long slide to the user when published?

Or does anyone have any tip/suggestions on better managing super long slides?

Thanks.