I think we'd need to ask someone who actually knows what they're doing about fermenting it out dry or perhaps changing the yeast to one that denatures at a lower ABV %.
I had one of those ebay kits (which turned out to be little more than brewers yeast / ginger powder / sugar). Im keeping my eye on the proper one but Im not paying silly money for a science experiment.
I found another recipe for GB in an old (1973) book and that too has 1lb sugar per gallon so I suppose it must be ok... I can't find my usual brewing book but from looking at this old one I should have taken a SG reading at the start in order to be able to work out the ABV. Guess I'll just have to do the 'falling down test'.
It also contains a recipe for a GB plant (sorry) but that too is only bakers yeast, water, sugar and powdered ginger. Is this not the way they all start out or is there some special yeast to start them and is it supposed to taste better?
Ginger beer plant is a different beast to yeast. I have some growing on my windowsill - it's a symbiotic yeast and bacteria which floats about. Unlike yeast it sits in the sun, not in the dark and this keeps it in balance.
If you look around on the net, you can find a few places that do it. Mine just doesn't grow quick enough to supply people (loads of people keep asking for it! It's pretty rare!)
The difference in flavour is subtle from normal yeast - it has a more complex sweet/sour flavour. To be honest though, use brewers yeast, it's not an awful lot different!