I had this same problem a week ago.
First of all I noticed your URL has an ampersand preceding the parameter string, but it probably needs to have a question mark instead to begin the parameter string, followed by an ampersand between each additional parameter.
Now, you do need to escape your URL but also double-escape the URL parameters (title or other content you need to provide content in the Share) you are passing to the URL, as follows:
var myParams = 't=' + escape('Some title here.') + '&id=' + escape('some content ID or any other value I want to load');
var fooBar = 'http://www.facebook.com/share.php?u=' + escape('http://foobar.com/superDuperSharingPage.php?' + myParams);
Now, you need to create the above-linked superDuperSharingPage.php, which should provide the dynamic title, description, and image content you desire. Something like this should suffice:
<?php
// get our URL query parameters
$title = $_GET['t'];
$id = $_GET['id'];
// maybe we want to load some content with the id I'll pretend we loaded a
// description from some database in the sky which is magically arranged thusly:
$desciption = $databaseInTheSky[$id]['description'];
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title><?php echo $title;?></title>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="title" content="<?php echo $title;?>" />
<meta name="description" content="<?php echo $desciption;?>" />
<!-- the following line redirects to wherever we want the USER to land -->
<!-- Facebook won't follow it. you may or may not actually want || need this. -->
<meta http-equiv="refresh" content="1;URL=http://foobar.com" />
</head>
<body>
<p><?php echo $desciption;?></p>
<p><img src="image_a_<?php echo $id;?>.jpg" alt="Alt tags are always a good idea." /></p>
<p><img src="image_b_<?php echo $id;?>.jpg" alt="Make the web more accessible to the blind!" /></p>
</body>
</html>
Let me know if this works for you, it's essentially what did for me :)
