New to Mac OS and need answers for a few questions.

So... To begin, I'm all Windows for a good couple of years now, and finally made the switch as I was incredibly frustrated by Windows OEMs' lacklustre offerings. Like I said, I'm new to this and I'm still getting accustomed things. So naturally, I've got questions and I need help.

First of all, coming from an all Windows background, I've already started to face problems the moment I boot up my MacBook Pro. I wanted to set up Time Machine, but I've got only one 2TB external drive. So I shrunk my partition in Disk Management in Windows hoping to be able format the unallocated space with the HFS+ filesystem in Mac afterwards. As you may have predicted I am unable to do so as it uses the MBR partition scheme. Any better ideas?

The second question is pretty simple. Why does the OS consume so much RAM? Again, being used to running Windows and I know my stuffs, I'm used to seeing Windows consuming only around 500MB of RAM when I'm not doing anything. Now, you can imagine how shocked I was when I found out that my rMBP Haswell is consuming about 11GB RAM (out of 16) when I quit everything from the dock! Is this normal? I have Caffeine, Memory Clean, Scroll Reverser, f.lux, gfxCardStatus running in the background if that helps. Also I got no idea how to check what's running silently in the background (please tell me how if there's a way) so I am wondering can Parallels Desktop 9 and Adobe Creative Cloud be the culprit?

Thank you for taking your time to answer these questions. Your help is very much appreciated.