The font used in the screenshots is Fira Code.
To install this sytax theme go to the Settings > Install section, search for
One Dark Monokai and click Install. When installed the theme can be activated by going to the Settings > Themes section and selecting One Dark Monokai from the Syntax Themes drop-down menu.
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.