One simple method of determining the weight of each breast is by looking at the label on the package. Typically Purdue breasts are sold by the pound. If the package is one pound, and there are two breasts per package, then assuming they are about the same size, they are about 8 ounces a piece.
As far as a "low-fat oil", I'm not so sure there is such a thing. You are better off focusing on the type of fat in the oil. As a threshold matter, it may pay to take a quick look at your entire intake of fat, instead of just focusing on what you use as an oil for cooking. John Berardi gave this handy chart an explanation.
I cook with a combination of sesame oil and olive oil. I like the taste of the added sesame oil and it seems to raise the smoking point of olive oil a bit. For pancakes, I use canola oil in an aerosol can. It's easier to control application of the oil to the pan.