1. How do I truncate intro text in Featured Sliders (screenshot att.)? I already set Max Content to 200 characters in [Views >> Frontpage Layout >> Featured] but it didn't help.
I've checked in your site, it seems like your existing blogs got contain those readmore tag, so it will populate those content before the readmore tag on the feature slider, so it will not respect what you set that Max content character from backend setting.
I've modify this one of the Easyblog core file from your site then override into your current template
/public_html/templates/rt_audacity/html/com_easyblog/blogs/latest/featured.php , it should truncate the content correctly now.
2. Please explain what you mean by "you have to clear your CDN cache then start let it start re-cache back, then you only set back your CDN URL from Easyblog setting." Where do I do this?
To be honestly, I am not really familiar with the CDN thing, but based on what our customer told us, your CDN server should have 1 "Purge" cache button, what you need to do is click that purge cache button from your CDN server, once you done it, you can try insert back your CDN domain into Easyblog setting.