Sites scraping my site, serp rankings lost, what can I do?

I think you have done the correct thing by serving up a blank page. It looks like Google is just being slow to update. If those scraper websites have little traffic then Google won't be visiting them often and it could take months before every page is removed.

However, I would suggest removing the 'nofollow' on the page. With nofollow the link is not counting towards your site - if you remove it, your PageRank should be boosted a little more and help to keep you above future scrapers you haven't blocked yet.

You also said the scraper sites are removing all JS code but if you're able to put other HTML on the page you could consider either a meta refresh tag:

<meta http-equiv="refresh" content="0;URL='YOURURL'" />

Or a JavaScript onload attribute:

<body onload="window.location.href='YOURURL'">

According to this meta refresh is observed by search engines so again may speed up removal of the scraper sites.