A few points:

1. IMHO, the reference to Guido in the epigram is there not to suggest that Prufrock is about to embark into hell (as Eliot's various characters in The Waste Land will, for instance), but rather to draw a psychological parallel between both the pain that both characters feel in retelling their story and the hesitence that both has to retell their stories due to their fears of judgment from others. Guido is the first character in the Inferno to specifically request that his story not be retold in the world above; what Prufrock shares with him is an (undue?) sense of shame.

2. I had read that the lines about women talking about Michelangelo were there for two possible reasons, both of which are ironic: either it is I. a purposely erroneous passage meant to display how uninformed or idealizing Prufrock's character is (i.e. the women are *really* talking about something more simple and day-to-day than Michaelangelo, and the clueless Prufrock can understand neither them nor their interests) or II. These women really *are* talking about Michelangelo and are themselves totally unconscious of the raw sexuality of the painter's fleshy images.

3. The yellow fog is, I believe, inspired by Carl Sandburg's Fog, and is there in order to set atmosphere.

4. Prufrock worries about rolling up his trousers because it is I. a sign of old age and II. neccessary if he is to walk on the beach without getting them wet.

5. Finally, although Prufrock does know that he is not capable of Hamlet's final heroics, he is perhaps aware that major interpretation of the Danish prince's character find Hamlet's motive to correspond exactly with Prufrock's problem: indecision.