resizing is possible but risk is to high.
look at your harddrive, even thought its sold as 250gb it's really only 232, same with phone. it's the same on all phones, funny you only notice now.
Also yes is takes about 7gb partition, not sure but is a lot, so what you are left over with is a lot less. Again this is same on all phones, all manufacturers etc. good read: http://forum.xda-developers.com/show....php?t=2602234
ps, don't ota update when your phone is rooted and or running custom recovery btw.
Sent from my LG-D802 using xda app-developers app