Understanding fonts

Hello, I am working on some customization for my gitea page and almost have it to how I want. The area I am struggling with is font sizes which is due to my lack of knowledge of HTML/CCS I am sure.

I have set up my two fonts as follows in my root in theme:
–fonts-proportional: et-book-semi-bold-old-style-figures.ttf !important;
–fonts-monospace: ProggyVector Regular.ttf !important;

This works great where code is PrggyVector and all other text is etbembo. The only issue is at 100%, the text is slightly too small.

So far I have tried to add the following to the root section from researching CSS but have not been able to see any font size changes after clearing browser data or just making a new theme. Ideally I would just like to bump up the percentage of everything. Any guidance is helpful!

I have tried
–base-font-size: 300% !important;
–font-size: 300% !important;
I also have tried em, px and xx-large to no avail.