There are a number of sins listed above, that have a qualifying word or phrase attached, such as...improper behavior, extreme, willfulness, inordinate, excessive, etc. What or who is the reference for these subjective levels? That is what I am asking
The author is referencing, among other things, the “Catechism of the Catholic Church”. I have occasionally looked at it, to see what the Roman Church actually teaches on one or another topic ... it contains some detailed discussion of the various sins the author lists.
A useful discussion might follow if you were to pick one sin that interests you (for any reason, or no reason at all), and post the entire passage along with your comments on the matter.
In general, I believe that terms like improper, inordinate, or excessive mean something like “doing it to the point of causing damage”. Willful means knowing what you’re doing. And I think you’ll find, in general, that border between “excessive” and “not excessive” is fuzzy. I also think that, in general, if the average person would be worried about “is this excessive”, it probably is.