Setting are automatically saved. That’s why there’s no save button. If you’re not seeing your changes outside of Microthemer, it could be because you having caching enabled, which needs to be cleared (either a plugin or sever-level caching like Cloudflare).
Can I just check you haven’t enabled ‘Draft mode’? In draft mode, changes you make in Microthemer are not visible to regular site visitors.
Hey, if the styles aren’t working in Microthemer, it’s possible a theme style is overriding your Microthemer style. Or you need to target a different element. Would you mind sending me a link to your site with a description of which style isn’t working?