1 The ordinary meaning of לָכֵן (lakhen) is “therefore,” coming after an argument. But at the beginning of a speech it is an allusion to what follows.
2 The verb is שׁוּב (shuv, “to return”), but in the Hiphil, “bring me back,” i.e., prompt me to make another speech. The text makes good sense as it is, and there is no reason to change the reading to make a closer parallel with the second half—indeed, the second part explains the first.
3 The word is normally taken from the root “to hasten,” and rendered “because of my haste within me.” But K&D 11:374 proposed another root, and similarly, but closer to the text, E. Dhorme (Job, 289–90) found an Arabic word with the meaning “feeling, sensation.” He argues that from this idea developed the meanings in the cognates of “thoughts” as well. Similarly, Gordis translates it “my feeling pain.” See also Eccl 2:25.
4 There is no indication that this clause is to be subordinated to the next, other than the logical connection, and the use of the ו (vav) in the second half.
6 The phrase actually has רוּחַ מִבִּינָתִי (ruakh mibbinati, “a spirit/wind/breath/impulse from my understanding”). Some translate it “out of my understanding a spirit answers me.” The idea is not that difficult, and so the many proposals to rewrite the text can be rejected. The spirit of his understanding prompts the reply.
7 To take this verb as a simple Qal and read it “answers me,” does not provide a clear idea. The form can just as easily be taken as a Hiphil, with the sense “causes me to answer.” It is Zophar who will “return” and who will “answer.”