Display all Nodes associated to a Taxonomy term?
You could accomplish this by writing code (in a custom module) to ajaxify the relevant select fields. Check out the Examples module (ajax examples -> dependent dropdown) for implementation help. Here's what needs to be done roughly:


Use hook_form_alter or hook_form_FORM_ID_alter to add necessary #ajax options (callback and wrapper at minimum) to the taxonomy select field. The node reference field needs a wrapper (via #prefix, #suffix) and #options changed when a term has been selected (value set in $form_state['values']).
A function for the ajax callback returning the node reference form field.
Custom functionality checking which nodes are associated with the selected term to set the right options for node reference. Easiest way might be by querying them directly from the taxonomy_index database table (if you need other data (like type) include the node table as well).