This theme has awsome potential but it’s just not quite there yet.The color scheme, though grey is eye catching and so is the whole menu thing opening up.However, once that menu opens everything goes downhill from there.The sidebar info just looks kinda thrown in there… not neat or orederly at all.
I also think you can throw some sidebar info down at the bottom as well so the menu space doesn’t become too cluttered.
Here is a site that in width is similar to yours and at the bottom he added space for the archives and recent posts- https://binarybonsai.com/ .
Here is another skinny site with a menu that opens up and looks great- https://www.thoughtmechanics.com/#top
You might also try taking a look at those css design sites to get some ideas.
https://cssbeauty.com/
https://cssimport.com/
https://cssvault.com/
Good luck ??