Resizing sparsebundle in Disk Utility
there seem to be a lot of questions around disk images, esp. sparse bundles and none of the answers I found here provide easy solutions.
You seem to have a few problems, I can help you with the first one (I ran into the same problem myself):


  Reclaimed 0 bytes out of 265.2 GB possible



Mount the image
Note the path to the mounted Volume, i.e. /Volumes/VolumeName
in Terminal type:


  diskutil secureErase freespace 0 /Volumes/VolumeName



For this step to succeed, there must be enough space left on the main Volume where the sparse image lives (I found roughly the space reclaimable plus a few GB to be a reliable rule of thumb.)

Then you can unmount the image and compaction should succeed.

freespace 0 fills the empty space with zeroes, all other options of diskutil secureErase freespace write random garbage to disk so other files are not recoverable. 

The rest of the commands should work fine now, at least for me they did... 

I realise this question is old and you most likely have moved on, but maybe it's a help to someone...