As for the widget area, yes this comes from theme, but widget area only displays widgets you insert into it, it has no effect on widget functionality. You can try to find a plugin that will provide you with a video widget with more advanced options.
However, I think maybe the best way is to use a page builder. Beaver Builder has a native Video module that supports autoplay. And using a page builder and building your page layout that way will resolve all your issues you experience here.
the suggest me to change the theme, and i dont want to.
I’m really surprised about this suggestion! Changing a theme will not resolve your issue as it is theme independent issue. It is related to widget functionality, not a theme. You would experience the same issue with any theme.