Help With An Imperial IPA

I'm new to all grain brewing and tried a small batch of Imperial IPA recently.  This one was a bit of a challenge and I would like some advice:

1.  When I initially brewed for a 2.5 gallon batch I did not account for boil off and wound up with a 1.0 (approx) gallon batch.  The O.G. of this 1.0 gallon batch was 1.1 O.G.  I boiled some more water, let it cool to 60 degrees, and added it to the wort the day after my boil.  I added enough to bring the total amount to 2.5 gallons.

Yesterday I measured the gravity and it was 1.005.  How can I tell the alcohol content of this beer?  Can I?

2.  At 1.005 this beer seems ready for bottling.  On Beer Smith it has "Carbonation 2.4 volumes" -- can someone give me a reference to better understand this?  I understand everything else in that section and am glad to have this information available.

Thank you!  This beer has been a real chore from the get-go but I tasted some of the wort after sampling the gravity and man, it is worth it.  Great citrus, candy and hops all at once.  I can't wait to drink a cold one!

    I use Beersmith to help me out with this but I've heard that you can   
subtract the OG from the FG, then divide by 0.75 (hope this helps)

When using your hydrometer, make sure the temperature is at 59 degrees to get an accurate reading.
stevemwazup

Let's try this -- can I tell how the addition of water volume on the second day affected my original gravity?