bobbyc, meads are wild and wonderful things, and as honeys vary dependants on season, source and age, so will your SG. You may have added too much water, but you didn't start with a whole lot of honey, either. I prefer to use older honey, so that less of its weight is water (crystalized). You may need a full 3 lbs of honey to give you a OG of 1.100. I make a lot of 1 gal batches when working out new recipes.
As to the amount of light, its not an issue, unless you decide to add hops to your brew.