I am looking specifically for text alignment (e.g. left vs. full justification) and what size/width text sections ideally have.
I don't believe you'll find oodles of research studies in the Web Style Guide, 3rd Edition, but one of the authors, Sarah Horton, has been in the field of web wusability, so I assume at least some of their conclusions are based on research. It doesn't hurt when Edward Tufte and Donald Norman recommend the book, either.
Anyway, there are two sections online that may be of direct assistance.
Each section relates to your concerns, although you may not find black-and-white answers.
Here is one lead: Web Page Readability / Usability Research, even if the title is web page and not web sites. It contains Font size, linespacing and text width among other things.