if it's jarring and kicking off bumps then your increasing the preload was probably a move in the wrong direction.
static sag is generally accepted as being set to 30 - 35% of suspension travel. setting sag is a useful starting point but is not an end in itself. it need not be that precise.
if it were me I'd set it to the handbook then ride it and adjust from there. from your description I'd back off the front compression by a couple of clicks and add a couple of clicks rear rebound then ride again on the same stretch of road. there is no golden rule - suspension setup is down to individual taste.
static sag is generally accepted as being set to 30 - 35% of suspension travel. setting sag is a useful starting point but is not an end in itself. it need not be that precise.
if it were me I'd set it to the handbook then ride it and adjust from there. from your description I'd back off the front compression by a couple of clicks and add a couple of clicks rear rebound then ride again on the same stretch of road. there is no golden rule - suspension setup is down to individual taste.