Samsungs are pretty standard, see paragraph 1.3 -
http://androidforums.com/threads/s5-lollipop-update-problems-dummies-guide.892800/
Android runs off of its own cache.
You can't use Android to clear Android.
Think of recovery just like a little operating system made just to help service Android.
Every time you've taken an OTA update where your phone rebooted, that was recovery at work doing the actual update during the reboot.
Just clear cache, reboot, and pull battery.
On a normally running phone, you'd lose nothing.
If your 10 GB misc goes away, it was already lost for good - the cache is on a completely different partition than any other data.
Otoh - your data just might come back.