I would've knockedとI should have knockedとはどう違いますか。
Yes, there is. In this context, "I would have knocked" means that Jerry is aware that he is being impolite by simply barging into the room unannounced. "I should have knocked" means that someone walked into an uncomfortable situation by not knocking on the door and regrets doing so. Ex: I would have knocked, but my hands are full. Ex: I'm so sorry, I should have knocked.
- すまない、ドアをノックすれば良かったけど、知っての通り私は暴力を嫌悪している。 - やあ。