1) I think it should delete/hide post form history as well or perhaps mark the record it in different color showing status "scheduled to delete". In this case option "Undo" would help (in case of mistakes), it would remove posts from delete queue.
Perhaps in this case can add checkbox "Show Deleted Posts" on top.
2) I also think no need to show second confirmation post as extra click is needed, This information can go to notification screen/log for example (if user wants to check).
3) Allow selection of multiple posts to be deleted from history by having checkbox next to it (perhaps new Select records mode / button). Than Apply to Selected "Delete Posts", "Delete Records" etc. Similar to the way you have on accounts screen.