The size is likely a browser (Chrome) issue, but you may be able to tweak it with some CSS changes.
First thing I noticed is that your video is contained in a paragraph with a style of “paragraph-style-1” – this is the same as all other paragraphs on your page, and likely that style is set to align text to the left, not centered, because left-aligned text is the default for paragraphs and is generally considered easier to read.
So you might try a couple of things – if you don’t want to modify your Theme’s stylesheet, you could wrap your video in a DIV and give that DIV a style of text-align:center, like so:
<div style=”text-align:center;”>(your video embed code here)</div>
Sometimes just wrapping it in a <center> tag works also:
<center>(your video embed code here)</center>
As for the size, be sure your video embed code is declaring a size – otherwise the browser will decide what size to display it at – if it doesn’t, see if there is a setting at Vimeo when you create your embed code, and if not, include a size in your style for the div:
<div style=”text-align:center;width:600px;height:480px;”>(your video embed code here)</div>
That may or may not work – here you’re just setting a size for the DIV, not the video, but it’s worth a shot. If you’re still having trouble after this with Chrome, try posting your question in the support forum for Chrome over at Google,
https://support.google.com/chrome/?hl=en#topic=3227046
