Minimal travel is needed to dirt jump. I personally run a 2006 Marzocchi Z1 sport that has had it's travel reduced from 150mm to 65mm permanently, and I run it extremely stiff. More travel than that doesn't help as it sucks up all your energy when you're going off the jump.
At your weight, if the fork feels too stifff, it's normal. You are not heavy enough to make it budge much. As you get older and heavier that'll change.
If you're bottoming out the fork all the time, then you'd have to buy a new fork, as there are no replacement springs that are stiffer for that fork, so you're stuck with what's in there.
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