Re: advice on sailing around Cape Hatteras?
Lots of advice here to which I can add very little having only done the Hatteras thing once. I would add, however, that 15 March might be a tad early. A month later would probably make for a better trip, especially if you're doing Hatteras to NY in a single hop.
If you're planning on stopping in Greenland you probably don't want to be there until the end of July, so that should give you lots of time to make your way north.
I'm planning on leaving Cape Cod around 15 June bound for Scotland. We may bump into you if we end up taking the northern route.