"If I had a Nickel for every newbie thread named that..." X_X

I just started playing Guitar (IE:Failing Guitar) earlier this week, and though I generally suck at it now, I'm getting better each day and really intend to take this seriously. As such, I have a few questions, and a very easy riff I made will be included Yay Me! :P

So far, I've really only used the Top E string; The Guitar's in Standard tuning I believe, but I can't be sure because my friend "Tuned" it but he claims he doesn't know how... X_X'.

The Top string (As I'll refer to it) sounds the best for the Riff's I've been playing, so I have not deviated from it. The Amp I'm using is pretty dinky, and I can't play Chord's unless the Gain is completely turned down; Even then it sounds bad.

Anywho, I've been trying today, to incorporate the 2nd string into my playing, and....It's fail worthy. I can play decently on 1 string, but when I move to the 2nd one, poop! My arm just doesn't wanna go down to the other string!

The question: How can I go about adding more of the Guitar's strings into music, and without my arm crapping out on me?

2: Following up on the first question, Is it truly necessary to involve 2, 3 or all 6 strings into music, or is that only important once I've gotten better on 1 string?

3: Though I'm amazing at Rock Band and Guitar Hero (Don't shoot me please), as in being able to move my fingers around fast and accurately on the Fret keys, I can't seem to do this on the actual guitar. It feels like when I first began GH/RB; My hands and wrists tire out very fast even though I'm doing the same basic motions.
How can I increase my Finger movement speed, or reach the speed I have on said games?

4: Nothing special here, just wanted to display the best thing I've done so far...Well, 2nd best. I have a band going with one of my friends, and so I've been trying to do Guitar riff's while I write lyrics; This is the lovechild of Me, the Guitar, and 15 minutes:


Hope I typed that in a readable manner X_X' It's only the Top string, and the first 3 frets + the open string itself. I purposely grouped it like this to try showing the rhythm, but don't misinterpret it and try to play the "01122" Fret because (I think) no guitar has over 1000 frets :X
Gentle criticism please? X.X