If others have something to share, they will follow and append to this thread.
Google Play has nothing to do with this issue. You are uploading to Google Drive. It appears that you attempted that, but only the slide and the VPJ file succeeded. But, if your project is a big one that will take 6 hours to upload, then don't bother.
Yes, the video shown in the above demo isn't yours, except for the slide. But it demonstrates that the slide can be placed onto track 2 directly above track 1 video. If there is no video on track 1, then it can be dropped above your audio on that track. Audio won't be touched.
If an image is placed on track two it will indeed be visible in SEQUENCE preview mode, just as seen in the demo preview window. Be sure that you are viewing the sequence and not the clip. Click in the timeline, or click the Sequence tab above the preview window. 
When the sequence is played, it will show the image - whether it's on track 1 or 2 - and play the audio. Same for the exported file.
Note that Fantasy In C is immediately above the first audio, and that it is shown in preview. No gaps, no shifting of audio...

This now appears to be what you're after. Achieving it is very simple in Videopad, per the above instructions.