Summarizing the important bits, as best as I could gather:
Font size is usually around 16 px for mobile, and 18 to 22 px for desktop. Remember, this varies based off of how big the font seems to be (different fonts can look different at the same size). It is recommended to match the size of text in a book. Lines should be around 45 to 75 characters, including spaces. Line height should be between 1.3 and 1.7 times the font size.