I wear my white DJ on all cruises but one tip try and avoid a burgundy bow tie as to my horror on one RCI cruise all head waiters wore white DJ's and burgundy bow ties on the formal nights (the tips were good though.
A standard 'white' DJ is normally ivory & yes you would wear it to a black & white ball.
Strictly speaking no but I think that no one will raise an eyebrow if you wear a white tuxedo but preferably with black dress trousers not white and yes ivory or very light cream will pass muster as well... Nei.
A white Tux is absolutely fine, indeed, adds that little extra. Most whites are now almost a shade of ivory, do be carefull on how white your shirt is though, it may clash if your tux is a touch darker ivory. Dress for success, have a ball. Richar.