In the latest developer version you can delete it 🙂
If you want to see it for yourself; download it, go to settings, scroll down to the Shortcuts section, click the Configure Shortcuts button, scroll down to Speed Dial and delete the Ctrl+Space shortcut.
We can't interfere with Sidebar size, at least not yet... I hope they implement 2 options; width state for each extension and auto-hide. Anyway it's a really good start 🙂
The same just happened to me! And now there's not too much I can do but create a bunch of new folders for all the mixed up bookmarks, which again will sync adding folders where I don't need them to be... How come selective sync is not featured since launching?? This one is a must, otherwise sync is pointless.. Really hoping that this fix will be included in the NEXT update.