Random questions from the last part of the chapter:

1. Does the blocking of the Gate suggest the Company was lead into a one way trap?

I'm going to vote "no" because I think any trap would have been sprung sooner. As it is, the Fellowship nearly makes it across Moria before they are pursued by anything other than Gollum. I think the Watcher was either a predator just after food (nothing to do with the Ring at al), or being evil it was drawn to the Ring for itself. The latter is what they go for in the film - I think I remember from the documentaries on the DVD that they see it as after the Ring for itself and show it holding Frodo up to search his pocketses. One of those "Oft evil will shall evil mar" moments, to quote Theoden's proverb .