At the moment it's much safer than most other CMS's, as there is no admin backend to hack into. A hacker would need access to your actual server to change a Baun site. So hopefully there should be no headaches.
We don't have a demo but http://bauncms.com is built using Baun. Despite having similar features to Pico, this is a complete rewrite using modern PHP standards. I sold Pico a while ago and sadly the project seems dead. I'm hoping to go much further with Baun.
I think you're talking about a carousel (showing multiple slides at the same time). This is technically an "image slider" so is designed to only show one slide at a time.
You could just create a static HTML site yes, but getting it generated for you from Markdown files is super handy. To generate it on the fly it needs to be powered by some kind of server (e.g. Node, PHP, Python etc). Nodejs was just a good choice of platform for this kind of thing.
No, I don't need another static blog. I mean (bi-directional) cross reference is very important for memorization and even better than a simple search engine. Maybe you can use Disqus comment box to get related article but that's not good enough.