Is the understanding correct that the phrase "it may be that he took it, and if he began with the wording of Allah's speech" means benefiting from the wording of Allah's speech, and not taking the letters of Allah's speech themselves?

The meaning understood by the questioner—that the letters of Allah's speech were not taken by the speaker and do not subsist in Him—is correct in itself. Shaykh al-Islam Ibn Taymiyyah stated that those affiliated with the Sunnah differed regarding the letters of the alphabet outside of the Qur'an. Some said they are created (meaning, the letters are of two types: those within words and those pronounced individually), while others said they are uncreated (meaning, the letter is of one type: it is part of Allah's speech) because they are part of Allah's speech. Ibn Taymiyyah held that the dispute was verbal. Whoever said they are uncreated meant that they are included in Allah's speech and are the material of the لفظ (pronounced word/utterance) of Allah's speech, and this is uncreated. As for the isolated letter, it does not exist except within what forms words. The letters pronounced individually, such as "alif, lam, mim," are the names of the letters. So, if a person speaks other words using the letters of the alphabet, they pronounce letters similar to those in the لفظ (pronounced word/utterance) of the Qur'an, not the very same ones. Ibn Taymiyyah mentioned this statement to clarify that the letters are not created, and he emphasized the obligation to affirm that the letters of human speech are created, unlike the letters of Allah's speech.