gm
1. Your rewrite rule shouldn’t be necessary. You should already have:
RewriteCond ${REQUEST_FILENAME} !-f
RewriteCond ${REQUEST_FILENAME} !-d
in your .htaccess file before each RewriteRule. This tells your server not to do any url re-writing for real files and directories.
So, within MODx you need to refer to all real files with the standard URLs: eg:
http://www.site.com/assets/images/...
which you can do like normal: [(site_url)]assets/images/...
I suspect that you have probably specified a multilingual root,
http://www.site.com/lang/, as the base href meta tag and are trying to refer to your images using relative URLs. If so, try switching to [(site_url)] or (yams_server) as your base href or using complete URLs throughout.
2. Hmm. I have never seen that before. Perhaps you could tell me a bit more about your YAMS set-up. Which combination of server-name mode, root-name mode and/or query param mode are you using? (See the Language Settings tab.) Also what version of YAMS are you using. (See the Documentation tab.) Are you getting any errors in your php error log or within MODx under Reports>System Events when you try to access the preview?
Cheers.