Embedded YouTube videos question

Hi all,

I’m just in the beginning stages of designing a new website at https://www.mixmethods.com which will feature videos with recording basics, tips, info, etc.

I was doing some tests with embedded youtube videos and I am running into an issue. I set a size for the video and it fits nicely into my margins on the page. I checked it on the several computers in my home and it looks nice.

The problem is, I checked it on several other computers elsewhere, with various screen resolutions, and the embedded video size is not consistent. It is sometimes too big and covers up the sidebar. Obviously, this makes it much less professional looking.

I also noticed some small formatting changes on some other computers/browsers that changed the location of items on the sidebar.

Any suggestions on how I can make my content (especially the youtube vids) more consistent among various browsers/resolutions?

Thank you! (Also, any suggestions on overall design, aesthetic or technical, are much appreciated!)
Nate