Finding it difficult to control font weight of custom added font (variable font) on Flatiron 7.0 site.

Site URL: https://www.codylafond.com/

I've managed to add a custom font to my site (Flatiron 7.0 template) but I can't for the life of me sort out how to control the font weight. The font itself can vary from quite thin to quite bold when used in Adobe programs, however it exclusively appears in a medium weight throughout my site and I cannot sort out how to get it to appear bold in some instances and thin in others. 

I suspect it may be due to the font being a variable weight font. I've tried specifying the font weight in CSS (ranges from 100 to 800) but it won't take effect.

Any advice on how to approach? 

I'm having the same issue with my site... Have you find a solution since April?