ISO 1600, lowest aperture and longest exposure... you could not have done anything more to get more light in anyway.
Considering how dark it must have been, I think you have exposed it pretty well.
You probably did it anyway, but whenever I am taking a long exposure, I stick the camera on the 10 second self timer so that it has settled properly between me pressing the button and the shutter opening. A remote control is better as you also get the bulb function but I can not be arsed to buy one for the one or two shots I might use it for.