1) Nothing is wrong here. It is actually working exactly as it should. You change entity name but you don't provide it with new sprites. Editor doesn't rename your sprites for you. It also doesn't clear sprites when you remove decoration just in case you removed it by mistake. I'll try adding something like an auto renaming.
2) Perhaps. I'll check it.
3) It is. Probably. But I won't even try. It will definitely introduce new bugs and I don't want that.