The font and other css properties can be overwritten using your own css file.
Add the following parameter to your map: css=<url>. An example is: https://www.easymapmaker.com/map/58890adb2af63457f31769e607d7501f?css=https://www.easymapmaker.com/cssoverride/hideimg.css
The url must start with either https:// (preferred) or http:// and the url must exist to be included.
To change how the map itself looks (hiding roads or changing the color of the map), the map can be styled separately from the css: https://www.easymapmaker.com/features/map-style/