Hey,
glad to hear the font upload now works without problems.
If styling does not seem to be affected by your changes there is a chance your cache is not updating/invalidating when you make changes, and thus serves old files. On my sites I’ve used a different caching plugin, so I can’t exactly give you instructions on how to refresh your cache, but the plugin should have options for that. The one I use, for example, doesn’t generate new cache files for logged in users (admins) unless to specifically enable it to do so. Also, if you are using an external CDN cache like Cloudflare or the like then their remote cache also needs to retrieve new files from your site for caching, after they have updated on your server.
Fontsampler is not very restrictive in its own styling, meaning where sensible it will inherit values from your site, like font color, family, styling of general level elements like html tags etc. If you find something in particular that seems off let me know or provide a screenshot or link so I can do some more investigating.
