I think you are right. There are many synonyms for the idea that something is finished that can have different implications. You could say: I did my work. My work is finished. I finished all my work. I did most of the work and my friend helped until the project was completed. The exception would be if you were describing a story in the past and needed to indicate that the work had been done before the historical time your story is about. ie, we painted the walls when the the first coat WE HAD PAINTED was fully dry. In common conversation, I doubt you'd have trouble being understood if you opted to use the simple past version. https://www.ego4u.com/en/cram-up/grammar/simpas-pasper

I think part of the interpretation depends on he setting you asked the question in: his office privately or in front of the classroom. Many professors spend a lot of time reading many, many essays and doing their best to be fair even though it becomes more challenging as they get tired or frustrated. Your particular question was not a badly worded question, I think the suggestion I would put forward would be to reconsider your approach to consulting your professor. If you met him in his office and stated something more along the lines of "I wanted to thank you for your feedback. I was wondering if you have time to look over this part with me as I'd like to understand." Opening the conversation with open-end questions might give the professor the opportunity to tell you what they were looking for and they will likely refer to the section you are more proud of. In your original line of questioning, it sounds like you began with an accusation. I'd recommend seeking a private meeting (office hours) to be ready to hear what they want to tell you and coming prepared to listen with a minimal number of specific questions. If the teacher is seeing a pattern in your writing he/she is trying to focus on and help you with, that would be a less frustrating was for both of you to understand and move forwards :)

In regards to the character blinking though the narrating character (Skeeve) wouldn't have seen... it's another example of the author "painting" the setting for the reader beyond what pure dialogue can accomplish.

'Loomed" is a reference to the character, the Keeper's, size and personality. Looming is foreboding. It implies intimidatingly large size with possibly ill intent .... see ""the keeper growled"