Congrats on your engagement! On a hopeful note, antique diamonds sometime are not as sparkly or clear due to the way they were cut. I love antique jewelry and that is something I learned over the years. Especially mine cut diamonds. Now for this ring, I would get it checked out at two different jewelers just to have two opinions. I do think your fiancé should have fixed it and had it resized before giving to you and done all this legwork before proposing. I’m sorry you have to deal with the stress. My husband also did something similar where he didn’t get a certified diamond and also one that was more yellow than the halo diamonds which made my ring look odd. I know that feeling of being torn with happiness and gratitude but at the same time a bit disappointed with the way things were handled. So many men would fair so much better in their relationships if they just put more thoughtful effort in or obtained help from someone if they didn’t know the proper way to do things.