Mac Crashes During Boot Camp Assistant Disk Partitioning The other day I was using Boot Camp Assistant to partition my 2015 MBP to dual-boot Windows 10. I came back to discover my Mac was had just crashed and rebooting. I knew this could have gone very badly. Nothing major seems to be broken, however I had to use my old password to login (I changed it only days beforehand, and I haven't needed to use it since). I was using the 64-bit ISO file (stored on my computer) from the Windows website.

I have a few concerns:


I have 256 GB of memory, but my Mac shows I only have 209. Is some missing due to the partitioning?
What do I need to do in order to get Boot Camp Assistant to function properly?
How can I repair any damages that occurred due to the failed attempt?
209 GB usable space is normal for a 256HD.  It has to do with formatted partition sizes plus the hidden recovery partition.  Totally normal.
It will likely crap out again.  Not sure why.  To fix it, you'd need to look at log files (Applications/Utilities/Console) system.log and see if there's any error or at least what its doing.  Fixing it will be a total PITA.  The most direct way to fix it, will be to back everything up, boot from an Internet Recovery (not the local recovery) and totally repartition the drive using Disk Util.  Then put the Mac OS back and your data back.  Then do it again.  
Hold Command-R at boot to boot up the hidden recovery partition.  In there, use Disk Utility to check the disk for errors.  Don't format, partition, or erase your disk there - that'll kill all your data.  Hopefully, you have a full backup before starting any of this process.  good luck!