Is there a term that describes the degree of how much actors break the 4th wall? E.g., how frequently and how long they do so.
The terminology that Community creator Dan Harmon employs is "meta," used as a comparable adjective. In a 2010 interview with Uproxx:
“We don’t go to our Thursday night half-hour shows hoping to have our illusions subverted,” he said. “We don’t hope someone will kick us in the ass and say, ‘You’re watching television, stupid! Stop doing it!’ We go there because we want a half-hour break, and we want to escape into a place that has a fourth wall… How meta is too meta? The answer is simple: it’s too meta when you’re being punished for watching the show.”
The title of the article is "For 'Community,' How much meta is too much?"—using "meta" as a noun. But Harmon's version seems to be the more prevalent: As of January 2018, "how meta" gets 167,000 Google hits, to "how much meta"'s 8,100.
Adjectival "meta" is very useful for comparisons of this type. We can say, for example, that later episodes of Community were more meta because they referred to the show's tumultuous production history. Parks & Recreation is more meta than The Office (for my money), because while characters acknowledge the camera/viewer in both shows, The Office rigidly follows the documentary conceit that Parks & Rec doesn't think too hard about.
We can even argue that House of Cards is more meta than either of these shows because Underwood looks right into the lens, while talking head segments on The Office and Parks have characters typically make eye contact with "interviewers" somewhere off to the side.
These examples are all subject to opinion, interpretation, and discussion. But using "meta" as a comparable adjective makes that discussion a lot easier.