How to monitor icloud backup progress? How to monitor icloud back up progress? 

I have left my phone plugged in and locked for four or five nights now. The backup has still not completed, but my icloud usage is around 45GB according to https://www.icloud.com/#settings. Does this mean the 45GB of data has successfully been transferred to icloud? Or that 45GB of space has been allocated, but all the data has not necessarily been transferred yet? When I go to icloud photos, they seem to be more or less all there, but I don't know if they are the full versions of each photo.

When I try to manually back up, it changes from "9 hours remaining", to "7 hours remaining", to "11 hours remaining", etc., even when I leave the phone plugged in overnight.
After 5 days you might need to figure out where the backup is hanging. 45 gb means you have significant data getting backed up. Also, there’s not a good way to monitor things, so you might need a a split half search. 

In this case I would disable backup of half the items and then see if backup completes in an hour or two. If not, disable half of the remaining items and repeat. 

See this article for how to selectively back up some apps and data. - https://support.apple.com/en-us/ht204247

Once the backup succeeds, re-enable things half by half. 

Worst case the backup never works and you have to back up to iTunes. Best case the smaller backup gets you past the log jam.