The theme of this section is that the value of life lies in what is accomplished, so that it is more appropriate to celebrate the end of a person's journey than its beginning. However, external accomplishment is not emphasized -- building, acquiring or even planting -- but rather the transformation of one's character which can be accomplished using the challenges and opportunities which are afforded to us. Hence, by paying attention to what looks important in death, one can improve the heart.
The sound of burning thorns is all crackle without much useful energy.
This phrase seems to indicate the awe of God can come from either side of a dilemma. The phrase could also be translated, "Do not relax your grip, since awe of God can go out with all of these." In other words, the sentence simultaneously indicates that reverence for God could dissipate (go out) as well as it could flow from one or the other.
Here the word "Kohelet" is used with a feminine verb, so the meaning seems to be "a gathering of women" rather than Kohelet, "the gatherer".