Leialeial Hi. Also using inkstone.
1) You can edit and change the cover. After you explore your novel, there will be a cog on the upper right of the browser that appears in the page of inkstone. Click that and you can view the page when you created your novel. Edit the cover, title, etc.
2) word count only updates after you save. I don't know what you experienced but my word count in word and inkstone is the same.
3) There is no way to delete. I think QI is going to implement that later along with other additional tools for inkstone. But that comes down the line. not included in the may 15 update.
4) It depends on your browser cache/history. I've already updated my cover twice since they were drafts. It only shows the first version until I clear my cache so it downloads it again. But the setting of the novel already show my updated cover. FYI. And I thought you were unable to upload a cover?
Hope that helps.