Haven't done anything like that, just thinking out loud here; I'm only talking about the 50s clips as an example:

- Instead of having one 50s image, have ninety of them on top of each other so that only 1 is visible
- Insert all ninety sound clips to the slide, but out of sight, i.e. out of the 'slide work area', so that they won't show in Slide Show View
- In the Animation Pane, delete all the 'Pause' animations so that only the 'Play' animations remain (this is just to declutter the Animation Pane, since you don't need the Pauses)
- In the Animation Pane, select one of the Play animations >> in the Animations tab, go to Trigger > On Click of > select one of the 50s images
- For that same 50s image, add a 'Disappear' animation, set it to 'With Previous' and drag it underneath the triggered Play animation
- Do this for all clips & images
- This way, when you click the 50s image that's on top, the image will disappear and the clip will play, revealing the image underneath that is triggering another clip when clicked
(I tried it on a slide with a few circles on top of each other, triggering videos and disappearing so the next one could be clicked, and that worked)