I was able to do this, but it took a few steps to do so.
First the querystring must be changed to get more posts. This is found in the newstweet-ajax.php file line 8:
$url = 'https://search.twitter.com/search.json?q='.urlencode($_POST['searchterm']).'&rpp=3&lang=en';
Change rpp=x to be the number of posts you want to get. You can paste this into your web browser to see the results.
Next, I don’t think that the new results will all appear (though) I’m still not clear on this.
In the news-tweet-utils.js file, you need to add the items to show. See line 82+.
jQuery(document).ready(function(){
jQuery(".x").show();
jQuery(".0").fadeIn(2000);
jQuery(".1").fadeIn(1250);
jQuery(".2").fadeIn(500);
//add similar code below to show extra items.
jQuery(".3").fadeIn(0);
jQuery(".4").fadeIn(0);
jQuery(".5").fadeIn(0);
jQuery(".6").fadeIn(0);
jQuery(".7").fadeIn(0);
jQuery(".8").fadeIn(0);
jQuery(".9").fadeIn(0);
That should do it.
As for your update rate, the setInterval code needs to be changed in newstweet.php.
var si = setInterval('gotoPoll()',60000);
60000 is milliseconds, equal to 60 seconds. So change that accordingly, but be advised you could really slow your page down.