Hello Wenyang, I think you are looking at an interesting point. If you would like some constructive feedback, I can think of a few things that might help your argument(s) or otherwise improve your paper.

First, you might want to consider distinguishing between idiomatic language and slang. You seem to have conflated the two, and I’m not sure that’s quite alright. Much work has been done on idiomatic language in academic English ( and it is specifically mentioned as something tested on Academic English tests such as the TOEFL because researchers have duly recognized it as an important part of Academic English - especially spoken English). For discussion on this, see the works of Frank Boers, or you can begin with a simple paper I did showing its importance in Academic English (https://doi.org/10.34409/apujlr.8.1_47).

Second, since you have Likert-scale questions, you should consider an SEM analysis, or at the least doing some amalgamation of items where appropriate and then conducting correlation analysis to see where commonality is in questions. I do not have a free SEM tool yet, but you can conduct a correlation matrix quite easily here: https://springsenglish.online/stats/ You can also get a video explanation if you are not familiar.

Ryan Spring Professor Ryan, thank you very much for your constructive feedback. I will make sure that I consider every single point you raised for my manuscript. Truly helpful.