Rule “fewer with countable nouns (less)”: This rule is too strict because “less” does not modify the noun “seconds” directly in “30 seconds or less”. See here: Liberman (2006).
Rule “Correct use of ‘cc’”: Some sources do accept the spelling “cced”. For comparison: “DJing”! I find “CCed” and “CCing” elegant because the capital letters already signal a difference in pronunciation. The apostrophe is normally used for elision (and possessive forms that are historically due to elision). Another possibility would be “to copy sb. in” instead of “to cc sb.”.
Rule “HIV virus (HIV)”: “The HIV virus” gets corrected to “The HIV”, but “HIV” without the definite article would be better. I also would accept “The HIV virus” – which elucidates that we are talking about a virus called “HIV” (while the “V” already stands for “virus”, readers do not necessarily know that).