Thank you for your answers.
Fermented to complete dryness, the maximum theoretical for OG 1070 would be 9.2% v/v. If you get 8% that's good enough I'd say. L
Try this wikipedia entry.
Kiteman your link is broke. Is this what you meant to post?
Nope, I was aiming at this: http://en.wikipedia.org/wiki/Original_gravity
Alcohol content is figured by taking the sg at the start and the sg at the end. The difference is % of alcohol. If your sg it the beginning then record it and when it's done you can figure out your content. Figuring the alcohol at the start is just a guess based on experience.