I know what you mean, my older stuff is still great but the styling and cut etc. make me look bigger een though I've lost 50 lbs and had everything taken in. Congrats on the hard work, and ya awesome angle/fit.
I wear my great grandfathers signet ring with our crest, each generation has worn it. So I think if you're comfortable with it go for it (bloodstone setting no all gold) but that black diamond thing looks like you mugged some woman and shoved her bad engagement ring on your finger. No offence.
No if you look all the oxford cloths are done with a box pleat and no darts, they cut them with the same features regardless of the sizing (slim or regular) they're trying to preserve what makes an ocbd an ocbd. The proper "dress shirts" ie. spread collars etc. all have darts in slim fit.