I never think DB with an open shirt collar works, even with overcoats. Time and time again I rather keep my tie on in the bar/pub/restaurant than take it off after work...or look in the mirror after putting an overcoat on and go back to get a scarf.
Don't wear a belt with your suit if you're getting married.
For shoes you should probably be looking at something like Loake 1880's range or Alfred Sargent. C&J are nice but considerably pricey these days.