The last one is, Can negative trust be removed?
The answer is yes, as long as it is not a fatal act, neg-trust can be eliminated. However, only people who have given negtrust can do it. If the negtrust provider can't accept your request, then don't force it. Because maybe you will get additional neg-trust.
Thats the thing If you have been proven not guilty then the one who put negative trust with you still not removing the given feedback then hows about that? I think forum works like decentralisation too. Even the argument is favored to the user ( given red tag) those who gave can't remove due to their ego or let say superiority. Unless they got influenced by popular DT to remove their tag.