Taxonomy is erased when adding item to new or existing node

I'm having several problems with this main issue:

1) If a node is edited to add an attached file, regardless of whether it was previously created or not, the taxonomy is cleared and has to be reset. Something about that call to "add another item" wipes it out.

Related issues with filefield:

2) The default state for an "unlimited" requires a page refresh to get the "upload file" option, which is the thing that wipes out the taxonomy. Is there a way to change the default state to show this upload button?

3) In a custom view page for nodes to show taxonomy tags and attached files, any page with more than one attached file with filefield shows up as a duplicate in the list. I'm not yet an advanced Views user, but I can't seem to force the display to list only one, and it seems to me there shouldn't be two anyway. (Content > list shows one, for example).

Bonus issue: :)

4) Is there a way to share fields between nodes? I can't seem to make the filefield that was created for the story node work for other nodes without creating lots of redundant filefields with different names.

Thanks for any help!