Good day, how are you gentlemen?

I have a nice dual-boot Kali/Win7 machine here. I followed some instructions from an online source (can't remember who) and used the space recommendations from that source for the Kali install. root has only 1GB of space available, and that's after some command line wizardry to empty apt-get cache. I have read several threads about this issue, but I am curious about something specifically:

Why did the instructions offer advice to put so much space in /home? There are 90+ free GB of space there, and why does everything I do fill up root, which as per instructions I only allocated the 10GB or whatever? I am new to linux administration and this is my first install and things have been going nicely, honestly, until I wanted to check out the metasploit framework and then I got a not enough space error. Can I move space to root, or can I set things up so that the vast unused space in /home is used instead?

Here is a screenshot, and hopefully you'll understand my frustration at having so much space RIGHT THERE but unable to use it as needed.Screenshot from 2015-05-19 11:07:03.jpg