Singular Home Network

Alright, this is kind of complicated so I'm going to break it into the categories what I have and what I want to do.

I have:
Windows 7 desktop with 8gb ram, 700gb in space, and a quad core processor.
320gb portable usb hard drive
13" macbook pro with 160gb hard drive

In my room I have:
Wifi for both my macbook and pc
ethernet connection for my pc

Out of my room I have:
a different wifi for my macbook
I can tether it to my phone for internet


Basically, I work on both my macbook and pc on the same projects (multimedia design) in different places and times--currently I use the portable hd to sync the projects when I get back to my room. Since I have so many projects, I only have about 10gb of space left on my laptop. I want to just use the laptop as 'my portable desktop' per se. Since my projects are gui intensive, remote desktop doesn't work very well (I've tried teamviewer). I want to centralize all of my files on my desktop, and somehow access those over the same network I have in the room or from across campus.

Whats unique is that my desktop pc does not go through a router, I have a direct external ip -- how do I set it up so it's like a "super nas" that I can access securely over the internet? I've tried ftp but I've only done it for one-time file-transfers, not opening and saving projects, etc.

I'd appreciate any input, recommendations, etc.