1) I think this is a request to change one item, but I am sure it will be followed by others.
2) We should change any and all of the others - if we have a (safe) way to find the mall minimum.
3) And yes - I think that non-discardable items should show "no-sell" in an "autosell" column, regardless of whether we have a mall minimum registered for them.
1) requires changing one number in items.txt.
2) requires a lot of tedious data discovery & data entry.
3) is useful, easy enough, and a sufficiently satisfying coding change.
I'd propose we do #1 and #3 for now, and consider how/if we can do #2 efficiently and safely.