Hey Sarah Ambrose,
what was the outcome of your search I am trying to carry out something similar (number 2 on your list) and the issue appears to be that I do not own the layer.
The CSV file updates itself with the refresh interval but the layer it is joined to does not update with this new information.
Is it possible to own the layer if it is from an external rest api where the csv is downloaded from? Or is it possible to add a csv file to the content page via a url?
Thank you!