If something is being moved on the drive itself, you are correct. If they are being moved, then the data stays on the source drive till completely copied to the destination then deleted from the source.
There is no proof that there is an alien megastructure around this star. However, it is interesting that the start dims the way it does with no known reason for it to do so. Tabby's Star is really an interesting case for sure. If it does turn out to be something like a Dyson Sphere then it would be really big news but doubt it.
Here is a much more interesting and less clickbait artical on...
Ignore the unallocated space on your SSD. It is 549MB of space so next to nothing. The other two drives have nothing to do with booting. The EFI/MBR on those drives is for those drives alone. Just clean them with diskpart (make sure to select the right disk) and initialize them. Then format and you are good to go.