The subtitles are the smallest ones, but here are examples of what the texts look like in-game. These pictures are taken at 1920X1080 resolution.

Let me know if it's too small, I'll ask my team if we can add an option to make them bigger ;)

We'll look into it then!
And yes, buying now will give you access to the whole game once we release it. Our target is in early May, we'll announce the exact date as soon as we know. Temporary option: There's a UI scale that can increase text's size, but it also increase the menu size.