First off, get rid of the evil stock progressive springs and get straight rate ones that are proper rates for you. That makes a HUGE improvement on that particular bike.
The shock has a short rubber dampner and the linkage ratio allows it to contact the fender upon bottoming. The only good way to control this bottoming problem is to revalve the suspension.
From what I am told, KX's have extremely light valving stock. No amount of respringing will control the bottoming. Trust me on this one, I tried:confused: . I have extremely stiff springs, but it just ruins plushness and he bike still bottoms.
At your weight and claim of "freestyle", I owuld recomd greatly that you get at least stiffer springs and if you want your suspension perfect, get it revalved.
Sorry that there is no "simple" answer, just ones that cost alot of money!:D