McCandless' life "hummed with meaning, but the meaning he wrested from existence lay beyond the comfortable path." Do you agree?

I do agree.  In Chapter 17, the author goes on to explain that McCandless distrusted things that came easily, demanding "much of himself - more, in the end, than he could deliver".  McCandless wasn't a philosopher despondent over the meaningless of life.  Although he rejected the traditional lifestyle and values espoused by his parents and society, he found meaning in his journey, in his challenge to himself to live on his own in the wild.  He was living his dream, and so his life really did "hum with meaning", and as his last messages evidence, he did find peace and fulfillment.  He was, however, unable to physically survive the rigors of the challenge.