The pattern to fit the 36" bust blocks to 39" so presumably, that gives you ease similar to that shown in the photo. These sts, especially the rib, are going to be stretchy. If you want to fit a 46" bust, I think that you want to knit to 46" and block to 49" for the same kind of ease shown in the photo. When you do a swatch in pattern and block the swatch, I think you'll get a better idea of how many sts to cast on.
DK is going to give you a larger sweater since DK knits at 21-24sts/4inches and the pattern calls for a fingering weight yarn (28sts/4inches). You could try a swatch with DK and see how much wider it'll be. Maybe you'll even be able to use the pattern instructions for a smaller size. Be aware though that the drape of the sweater will probably change.