If I can suggest the following option...
Firstly, go to the Player menu. Under Player Controls, tick the Seekbar box, and then select 'Allow Drag After Completion'. Now, you need to untick that Seekbar box (this seems counterintuitive but stay with me).
By doing the above, it hides the Seekbar on all slides, apart from those where you have ticked the Seekbar option in the Slide Properties screen. Slides with this option ticked should only be videos, and nothing interactive.
When the learner gets to the slide in question, the seekbar will display, but they will not be able to drag it - at first. Once they have completed watching the video, the seekbar then becomes draggable (hence the 'Allow drag after completion' option). There is also a replay button that the learner can click at any time, to the right of the seekbar.
I don't know what's on the 3 layers you're talking about, but if you want to hide the Next button until the video is finished, just place a custom button on the timeline, and have it appear 5 seconds or so before the video ends.
I hope this makes sense!