So frustrating!!! No wonder you are discouraged.
I think the 8 looks a bit too big -- but maybe not if you scrunched the sleeves. And I think maybe the 6 is a titch too small in the shoulders. Also, I do understand what you mean about the length, although my own is that short and I am keeping it. I just decided that my knees are my knees and c'est la vie. I felt like if I made it look "grown up" in other ways, I was okay in it.
I actually think the colour is lovely on you. Maybe not as nice as a deep clear red, but still good.
But here is the thing -- if you are not comfortable in it, it's not a good dress for you. Your husband won't love it, you won't love it, you won't feel as pretty as you are, and that is double plus unfab.
Footwear is complicating the issue. As Jenn says, the smoking slippers read a little bit as, well.... slippers. Hose might help in this situation. But then you might be too hot.
I do think this style is great for you, generally -- but perhaps this particular dress isn't "the one."
At the same time, I can't help but wonder how things would look if you scrunched those sleeves. And could wear different shoes. Sigh....
Here is another direction to go -- if you are starting from footwear. Instead of a dress, go for "Le Smoking." Or an arty version thereof.
Black pants you have. And you could probably find cool silk ones (maybe even arty harem pants like Una's????) Add an amazing silk blouse in one of your best colours. Add bling and a fantastic clutch. And a topper if required.
How does that sound? I know a dress is still a HEWI (and EVERY woman deserves a dress that makes her feel like a million bucks.)
But in the absence of said dress, maybe "le smoking" would fill the dressy niche?