In Alexander Pope's "The Rape of the Lock," the "rules," as he describes them in "An Essay on Criticism," would not apply at all because "The Rape of the Lock" is not serious, but lightly satirical and humorous; the brilliance of the piece comes directly from Pope's choice regarding how to handle a strong disagreement between two families because a young man stole a lock of a young woman's hair. Plain language is used to convey ideas in a serious manner. People feuding over a snip of hair is ridiculous, and the topic begs for a playful hand, so much more in keeping with satire than plain language, and Pope provides this.
While the use of heroic-couplets is a serious and worthwhile tool of the poet, Pope's "The Rape of the Lock" uses something different. The word "mock," of course, sheds light upon Pope's attitude in writing this piece.
Modern critics consider The Rape of the Lock to be the supreme example of mock-heroic verse in the English language.
Although the two parties involved took the situation very seriously, Pope was encouraged to write the piece to restore goodwill between both families; he decided he would point out the silliness of the argument in a gentle way and have some fun with it. The blending of "heroic" and "comedy" allows the true nature of Pope's intent to shine through from the start. And structuring it as a great epic— comparing the simple act of snipping a lock of hair to the great epics of the past—allows one to gauge the true severity—or lack thereof—of this insignificant act.
The poem was intended to restore harmonious relations between the estranged families. Subtitled “an heroi-comical poem,” The Rape of the Lock treats the petty matter in full-blown epic style, which results in a great deal of humor.
While Alexander Pope's intent in using wit by employing plain language would create a more serious note in a written piece— especially where metaphors were not employed (therefore the writing would stand on its own merit without the artistry that metaphors allow)—the intent and subject of "The Rape of the Lock" could not possibly be written in plain language without sacrificing the satirical tone of the writing.
In An Essay on Criticism Pope uses "Wit" in two ways. In some instances, "Wit" means the poet writer: "Great Wits sometimes may gloriously offend, / And rise to Faults true Criticks dare not mend;". In some other instances "Wit" means intelligence or skill: "Pleas'd with a Work where nothing's just or fit; / One glaring Chaos and wild Heap of Wit;" "So Schismatics the plain Believers quit, / And are but damn'd for having too much Wit."
In your reference to "the definition of "Wit"," I believe you must be referring to this passage:
Some to Conceit alone their Taste confine,
And glitt'ring Thoughts struck out at ev'ry Line;
Pleas'd with a Work where nothing's just or fit;
One glaring Chaos and wild Heap of Wit;
Poets like Painters, thus, unskill'd to trace
The naked Nature and the living Grace,
With Gold and Jewels cover ev'ry Part,
And hide with Ornaments their Want of Art.
True Wit is Nature to Advantage drest,
What oft was Thought, but ne'er so well Exprest,
Something, whose Truth convinc'd at Sight we find,
That gives us back the Image of our Mind:
As Shades more sweetly recommend the Light,
So modest Plainness sets off sprightly Wit:
For Works may have more Wit than does 'em good,
As Bodies perish through Excess of Blood.
You'll notice Pope uses very many qualifying words such as alone, confine, every, nothing, glaring, wild. He refers to the poet to whom these qualifiers apply as "unskilled." He says this class of poet covers nature with "Gold and Jewels" over "ev'ry Part" because unable to show the "living Grace" of nature. This is a description of a poet who produces false poetry and Pope identifies it as full of extremes and extreme use of "Ornaments," what we call literary devices such as metaphor. It in necessary to note that in no wise does Pope disparage using literary devices, though he makes it quite clear he abhors the extreme overuse of literary devices to try to hide a lack of a poet's wit.
This answers your question then. While excessive use of literary devices, like metaphor and irony, is a mere cover-up for lack of intelligence and poetic skill, Pope admires the just and fitting use of literary devices such as the Greeks and Renaissance poet Wits gave such brilliant example of.
Therefore, in The Rape of the Lock, Pope was following in the "Rules" gleaned from his great predecessors and was most certainly not violating Wit through the witless excess of pointless "Ornaments" of literary devices as he described in the passage above.