You're making it much more complicated than it really is. Here's a simple demo page that does what you want.
http://misterneutron.com/JW5video/
And here's the page code:
<!DOCTYPE html>
<html>
<head>
<meta charset='UTF-8'>
<title>JW5</title>
<script type='text/javascript' src='jwplayer.js'></script>
</head>
<body>
<div id='myElement'>Loading the player...</div>
<script type='text/javascript'>
jwplayer('myElement').setup({
flashplayer: 'player.swf',
file: 'wildlife.mp4',
image: 'wildlife.jpg',
width: 640,
height: 360
});
</script>
</body>
</html>