Novice here. I am looking to submit a manuscript to a journal, Monthly Review. The journal website does not specify any template whatsoever except for the instruction to use Chicago Style, 16th edition for referencing. Should I include an abstract and a title page with a short bio in the submission (as is the custom in most social science journals I know of)?
Papers aren't normally published in the exact form of their first submission. I suggest that you write the paper as you think it should be written and submit it. Let the editor and reviewers decide if you should make modifications.
The title page is unlikely to be necessary in a first submission as it can be added later if needed (unlikely here). But an abstract might be helpful to the editor in choosing reviewers and to the reviewers in getting a quick overview.
But they will likely, in this case, ask you to remove them for publication. It is a process. Flow with it.
I think that you should write the paper just like you would want to write the paper. If you have editors, then they will make the modifications and tell you if you should add an abstract.
If your paper is long, then you should add an abstract to help the readers know what your paper is about, and a title page can be added later, that doesn't need to be done first.
If you do feel like you should include a title page and an abstract page, then by all means do so. If it makes you feel more comfortable, then do it.