I freed up 250GB of cloud storage but a week later it says I only have 95.6GB available

It probably can't resolve itself because there isn't enough space in your cloud account to handle what you have inadvertently asked it to do. All the images that you have stored in the cloud (more than 900GB when you started the clean-up?) through Lightroom on the MBP have then been copied down to the local drive through the "Store a copy of all originals..." option, but you've elected to store them in the CC Files folder. But when you add images to the CC Files folder they in turn are then uploaded to the cloud and stored in the CC Files space within your 1TB allowance, effectively doubling the amount of space needed in the cloud. But because you haven't got that much space, the CC Files upload pauses until more space in the cloud is available. So you've started clearing out Lightroom photos, which frees up space, which allows the CC Files upload to resume to start using up that space that you freed up. So as some data from CC Files on MBP uploads, it also downloads into CC Files on the iMac....which suggests that so far only 107GB of the 900+ GB in CC Files on the MBP  has been uploaded to the cloud. A long way still to go!

To put an end to this, I would suggest the first thing to do on the MBP is to uncheck that option to "Store a copy of all Originals..." on the MBP, which will at least stop the current download/upload cycle on the MBP. Then I would delete all of the data in those two folders in the CC Files folder on the MBP (Lightroom CC and Lightroom M1Max). That will take a little time, and that should also sync the deletions to the corresponding CC Files folder on the iMac. 

That then should return your cloud usage back to the 750+ GB that you are expecting.

Once that's done we can figure out how to proceed.