You can add some pre boiled water to the fermenter if you want. If it were me I would leave it and see how it turns out. You may have to age it a bit longer but it might be interesting to see how it comes out.
It sounds like you could use a brewing program like ProMash to calculate your brews. They are only about $20 and will save you the hassle of missing your gravity and SRM. Give it a shot. There are free trials for some of them so you can check them out before you purchase.