Hand Fatique When Playing Power Chords

I get serious hand fatique when playing power chords. I would use the index finger and pinky and after about 10 minutes of playing I got so tired my arm almost fell off. This is of course really bad in band practice because it adversely affects my timing... what is the least tiring way of playing a power chord?

Problems When Practicing Scales

I tried to practice the major scale (unfortunately during my years of just teaching myself the guitar.. I neglected to teach myself the major scale) My middle finger or the index finger always likes to hit the wrong note even at low tempo, causing my timing and rhythm to become totally screwed. I do this from time to time... any way to minimize this or perhaps eliminate it?

I really wished I discovered this site years ago...

Speed Seems To Be Stuck

I have a problem with speed... it seems as though there is a problem with my picking/fretting hand coordination and it severely limits my speed to about 128bpm at 8th notes (about the speed of the intro to "Sweet Child o Mine" by guns n roses) and it seems as though no amount of practice will improve that... I was trying to play a song called "Future World" by Helloween and the speed limit made it impossible for me to play that song, at least the intro riff.

I just started this site I decided that I am starting from the beginner lesson, now just getting the major scale down... I play bass now but its no reason to stop playing the guitar... im sure most great guitarist are good at both...