If your going to be system testing then you can't rely on figures after the fact, or best tote, or anything like that as a filter as they will not be the same when you look at them pre race.

The second thing is you can't compare returns from BFSP with best tote. They are completely different beasts.

Now to why your edge won't work.. The layers/backers on betfair do not have as much mug money thrown in with them so the prices are slightly more accurate. You will find regardless of what you find your slight edge will be adjusted for on betfair by slightly longer odds and you will lose around the 5% anyway (commission).