Yes, also forgot to say since it's kind of obvious that instead of removing the disk and cloning using another system you can just rebuild it, and in that case, save the old disk and run xfs_repair on the rebuilt one, and like itimpi mentioned you can use the GUI.
Not really, unclean shutdowns are the number one reason, I'm assuming you checked SMART for that disk and all looks good, maybe also a good idea to run an extended SMART test even if all look good.
I use btrfs on all my servers, mostly because of the checksums, and I believe it's stable especially for single disk usage, like unRAID data disks, still won't say that btrfs is more stable than xfs, the opposite is the consensus, so maybe a fluke but it's difficult to guess, especially without seeing long time diagnostics.
Are these ATA errors or cache full errors? maybe post an excerpt from the syslog, if they are ATA errors most likely the reason for the problem.