Hello Michelle,
Thank you for your question.
You are correct in the citing of bf 5.3.1 as a reference for your decision making. Deciding to retain or not to retain font attributes can be a challenge. My most important recommendation is to be consistent. If you decide to keep a typeform font do so for the entire book.
As for this specific example, keeping the font in the first paragraph is a good idea. You can also consider making the bold/italic words a heading to eliminate the need for any font.
I do not think that the font in the listed steps needs to be retained. I think the use of the colon is sufficient to set those words off. However, that does not mean that you cannot keep the bold. It ultimately is the transcriber’s choice. Just remember to be consistent.