I don’t fully understand the issue here - maybe you can explain some more. I’ve incorporated videos on a page and have not seen the issue with the dark bar at the bottom:
Can you explain where the videos are hosted, and what method you are using to display the videos.
The easiest way to have a play button displaying non centrally, is to make it a part of a custom thumbnail image. Alternatively, add a player icon over the video and have it act as a media control.