I like Wall Street Journal and their typography, https://wsj.com and how they write their articles. Not sure if it directly applies to Wikipedia, but I agree with your general point about typography - 80-120 character width seems ideal, any longer and it is tiring.

Perhaps we should go with columnar layout. I don't think it helps by adding a bunch of whitespace... ultimately, you're reducing the amount of information shown on a single page which could just be columnized.