Galvanic corrosion between nickel brass nut and stainless bolt I am planning to install something on a boat that will be in salt water, and my question is, will the nickel plated brass fastener not corrode if I connect it to stainless steel?

I looked it up on the chart and it says that there should be less then 0.15 V difference in the "Anodic Index" for harsh environments and while brass and stainless is within the 0.15, nickel is just outside.

The environment is not entirely harsh as well, as these will be used to fasten just the windows, so while there could be water there, mostly it will be fresh water from rain and the occasional spray from salt water.
While I cannot comment in a technical level, I can speak from a background in aerospace experience (in my family) and lifetime of building things that live outdoors.  

In time, dissimilar metal corrosion always sets in. Most stainless steels are inhibiting, not a 'way out' of the problem.  

On top of that, I think the ambient salts will kills you on this in the marine environment.  If you have a regular maintenance plan, then perhaps you can re-service the bolts yearly, as needed.