The Blackest Crow

I want to learn to play The Blackest Crow that Lisa posted on a discussion (don't know exactly where it is on here). It is in the key of G, ionian mode GGD. If I am tuned to DAD, how do I tune my strings to get to GGD. The melody I assume would stay on D, the middle string would go down one to G, and the bass string would go either up or down to G. Which would I go, up or down?

One more question. How come when I play the melody, it sounds like the tune, but when I strum across all the strings while holding the melody string down, it doesn't sound right. This is in DAD. Is there a way to play it in DAD, using the melody in this tuning.

The melody is basically 5-4-3-1-0-3-4-5-7-5-4-3-0-1.for the first line.

I'm not real good with music theory, but i know some.

Thanks for any help.