#1
Im having a bit of trouble figuring out which key i should be soloing in.
Ive just made a pretty cool little looping bluesy zeppelin bass riff.

it goes
G---------------------------------------------------
D---------------------------------------------------
A---------------------------------------------------
E--5-------3--------/(12)\-----0--3---------5----
1 2 3 4 1 2 3 4

I can't tab for shit, but i tried to get the point across.

Would this be E major? E minor? A minor?
"I think the most important thing about music is the sense of escape." - Thom Yorke
#4
Could be a variety of keys considering you're only using A, G and E however because you're starting on the A, I'd be more drawn towards A minor if it's a blues led zep bass line... however you could use C major/A minor G major/E minor D major/B minor F major/D minor as all of them contain A, G and E, instead of focusing on a key or a box position, try coming up with a melody in your head of how you want it to sound and mix it up a bit
#5
That bassline is currently in so many keys that you might as well just pick one and stick with it. I say go with A minor or E minor; just my suggestions.