This is not a rating out of 100, because it is not possible to reach 100 even with a 'perfect' fic. Hell, your scale as described can't even reach 75.

3)plot holes

minus 2 for every plot hole i find.

And if those plot holes are filled in a later chapter do you add those 2 pts back?

If not, than any fic you read is doomed to negative numbers unless it's rather short.

And what do you consider to be 'bad taste'?