1. The two parts of the tracker are the area to search for (solid box) and the area to search in (dotted box) The only reason to make the dotted box large is if your image is moving fast. If it's not, shrink that right down--you can even make it smaller than your solid box area. Often making both boxes smaller is the trick to getting a good track.
2. The exposure node has a cool trick for dropping the contrast to any color you want: pick the color you want (let's say 50% red, 18% green and 72% blue) and enter those values into the "pivot" section of the node. Now with "proportional" on, wind down your contrast and it'll pull towards that color. I've been using it to knock back shadows on skin tones lately.