I think the problem is not just down to the whitespace itself (whitespace is good), but the alignment and spacing of the items in the infowindow. In particular the rather raggedy right hand side and also around the title area where there is also a little more whitespace than necessary in proportion to the rest of the window.
You could try layout out the elements to give cleaner more aligned edges and the whole result will fill neater. You could also try banding the description area background to give the more button (and icons) a sense of their own space, and to draw out the ragged right hand edge of the text to the side of the box. You could also justify the text, but that has other issues with readability and awkwardness of spacing on narrow columns.
As you can see from the bottom of the map, I was able to shunt the vertical size down by 20px meaning slight less of the map is lost behind the window.
I don't think you need to worry too much about whitespace under the address, especially as addresses vary in length and complexity. And in any case there's also scope there to add other information (eg telephone number, popularity/importance rating, links) without further affecting the layout.
If you want to find out more about this sort of thing, read up on the Gestalt laws of grouping, continuance, proximity, closure, and related laws such as that of common regions and connected elements and I can't recommend enough the Universal Principles of Design by Lidwell, Holden and Butler.