You made it work! but all of above plugins rules are wrong!
You should have
RewriteRule ^ext/147d60d4/(.*) /wp-content/plugins/addthis/$1 [QSA,L]
instead of:
RewriteRule ^ext/147d60d4/(.*) /ext/addthis/$1 [QSA,L]
In case of fish4yours, it’s relatively easy to clone front end of a website but it seems they just park their domains to your site! This means you are safe and they don’t have any access to your files.
To ensure about it just create a new page in WP and publish it (for e.g. http://www.barwaldesigns.com/testing) then try that on that site: http://www.fish4yours.com/testing if that was there it means it’s just a domain parking and they are stupid hustlers!
It’s not really important but may take legal actions to that site by emailing to their host company or domain registrant (use Domain Whois)