@steter it's unlikely to be the base_url setting that's causing you issues, that's only used for RSS and embeds as far as I know.
I haven't used the preview server built into Faircamp.. I usually use --no-clean-urls and just open the .faircamp_build/index.html file in a browser locally. I run faircamp on a local machine to build the site then use rsync to publish to my server.
It's pretty good at showing you build errors with helpful information - are your builds successful?