I quickly glanced through the code, and you've got lots of problems. For example, you're using HTML tags, like font, center and u that were deprecated years ago. You're also not closing the <p> tags, among other things.

However, I'm reasonably sure that the video sizing problem isn't the HTML/CSS. I suspect that it's a javascript problem. To test out that idea, and since they looked suspicious, I removed the two "responsive" scripts at the bottom of the page, and the video displayed at its proper size. I put those scripts back in then removed the jquery script between your head tags, and again, the video again displayed correctlyt. I didn't bother analyzing the scripts themselves or check the rest of them, but it seems that some of those scripts aren't playing well with each other and somehow affecting the size of the video.

Thanks for checking it out. I never would have thought the javascript would cause a problem, I'll look into it further. And I'll be updating my HTML skills as well.