I also went from C5050 to D70 almost a year ago. I am sure you will like it very much. Ikelite i-TTL housing should be available pretty soon. As far as lens go, for macro, my personal favourite is the 70-180mm macro but Nikon has discountiued it and Ikelite does not support it. Of the 60mm and 105mm, I would prefer the 105mm but it depends on what you are shooting. For tiny subject 1-2 inches long and very flighty critters, you will have more working distance with 105mm. You will have to be very close to the subject for real macro subject with 60mm and lighting becomes a bit tricky. However the 60mm will focus much much faster, especially coming from C5050. I tend to use 60mm for nightdive.
10.5mm is a nice lens but incredibly wide so get close. Ideally it is good for hugh reefscene if you have great visibility or big creatures > 5-6 ft long that you can get very close ie less than a meter.
The 12-24mm lens is much more versatile despite high cost and not quite as wide but it is also a lot more fuzzy about port/extension ring combination.