"So" and "yet" as conjunctive adverbs rather than coordinators

Question

I have recently been digging into the "FANBOYS" concept and how "so," "yet," and "for" are not truly coordinating conjunctions in the same vein as the other four. Moreover, I have read that "so" and "yet" function similarly to conjunctive adverbs. If that's the case, is it acceptable to treat them like other adverbs and place them after a period/semicolon with a comma afterward? Or should they still only receive the typical FANBOYS treatment? For example:

He didn't want to come into work, so he said he was sick. (as a coordinator)

He didn't want to come into work, and so he said he was sick. (as an adverb alongside a coordinator)

He didn't want to come into work; so, he said he was sick. (as a conjunctive adverb)

I know the first is accepted as correct, but is either of the other two acceptable in a formal setting?

Answer 1

Dictionary.com licenses the resultative meaning ['and therefore'] of and so (though not the use of so itself as a coordinator in formal registers):

In formal English, so is not used as a conjunction, to indicate either purpose (he left by a back door so he could avoid photographers) or result (the project was abandoned so his services were no longer needed). In the former case to or in order to should be used instead, and in the latter case and so or and therefore would be more acceptable.        [Hence     •The project was abandoned and so his services were no longer needed].

.........

It also licenses the independent–clause-initial use of so (for sentences; this must allow for the use after semicolons):

Like and, but, and or, so can occur as a transitional word at the beginning of a sentence:

• So all our hard work finally brought results.

Stylewise, though, I'd personally avoid the semicolon usage as rather ugly. A comma, or a dash/ellipsis to signal a longer dramatic pause, in informal registers, or 'and so' in formal ones.