Hmm... I'm not quite as heavy as you, so what I say might not be applicable. It's a matter of building confidence. My first time down claremont I was freaked the hell out. The road quality was bumpy, the roads were narrow, and traffic was very heavy. My previous heavy downhills were mostly in Colorado, Utah, and Nevada, where the roads were wide, were excellent quality, and had nearly no traffic. I was pumping my brakes most of the way down my first time as well.
Now that I'm mostly a regular up in these hills, I only brake a bit just prior to corners. Given how my bike feels, I could probably blast down most of the way full speed as well, but I have yet to work up the courage. My brakes stop me plenty fast, and with a fair bit of control, I'm sure my brakes could easily stop me on the hill, although again, I'm not as heavy (170ish maybe?).
Here's something that's a lot more insane than going down on bike:
http://vimeo.com/1654340