Any pre load?About a third.
If you are able to get the desired level of sag with your current spring, that spring rate is correct for your weight. It sounds like the compression circuits internally will need work if you are still bottoming out hard. Going up a spring rate is not the answer you are looking for. Why did you not go harder on the low speed compression while you were out riding and still bottoming out ? I'd also suggest taking some high speed compression out as well.