How do I set a consistent, larger font size for all Finder directories on my Mac?

Somehow I changed the font in Finder, but strangely it's only for certain subdirectories. As I navigate from one directory to another, the font size changes depending on location. A quick Google search said to change the font in the Show View Options window. There's a drop-down for font sizes, the largest of which is 16. At that setting, my font is tiny on the screen. And the size is specific to the directory I'm looking at. Some directories, when viewed in the Finder window, have larger font. And here's the really weird kick - the Finder directories where the font is large enough don't have a value in the font size drop down. The value is empty, no value in the dropdown list chosen. Even stranger, there's no way to remove the value from the dropdown once a font size is selected. So the Finder directories with font that have a large enough font have a blank space for the font size. The smaller font size directories have been set to 16 for the font size, and that value can be changed from 10 to 16, but I cannot remove it entirely or enter a value manually.

I just want all my Finder window fonts to be the same, and large enough for me to read. My monitor's resolution is really high, so even at 16 my font is tiny on the screen.

[Re-Titled by Moderator]