A font replacement and even font scale change isn't impossible;
But I'd like to know what's actually needed as such to make it work well.
The first splash aside, what kind of font would you like to see? And would a font size slider help at all?
To clarify, what I want to do is an accessibility toggle; adding what you suggested - A transparent-ish black background to menus and anything with text, increasing the brightness of text. A brighter outline on the text is also fairly straight forward to add, I believe.
As for the musical note, I'll rework it most likely as I've gotten some feedback on the look of it. Do you have any other suggestions that'd make it easier for you?
Edit: To add to this, it would be super helpful if you could try and describe or let me know which parts were easier to read/see and which ones were more difficult, so I can get a better reference point for improvement.