My understanding is that there is no 1:1 correlation between weight and sit-bone width.
With your bone width, the Brooks B17 or C17 at 162mm width may do the trick for you (and the C19 is even wider). I have a C17 Carved and it is quite comfy out of the box for both short and long rides. In general I prefer a "hard" saddle with perineal relief, the padded saddles add pressure and friction in unwanted places.
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