60Kg and 330W for 20 minutes. Let's call it 310W FTP. Looks Cat 1 to me. Assuming you are a Cat 4 or 5, you should attack hills and should win/place in every race. I'm jealous. Just sounds like you need to learn how to ride the bike because descending at 18 mph when others are coming down at 35mph is a problem. Is your bike not stable at 30+?
Cat5. Just had my first "race" (HC TT) last Saturday. Keep in mind that both those 330/60 are on the optimistic side. Currently 320W is best 20' power, might be able to find another 10W but no guarantees. That and when I do a 20' test I do it fresh. My guess is that FTP for me would be closer to 90-92% of 20' power. I'd say 290W and 63kg is the safe option, 295-300W/62kg is realistic and 310W/60kg is on the optimistic side. I was close to 60kg running my best, but might be a little heavier now from extra bike muscle. I'll just have to see as weight comes off where race lean is.
Right now though weight is 68-69kg, so still a ways to go.
As for the descending, nothing to do with stability. I've just always been a very cautious, play it safe kind of person. Bottom line is I think I'm scared to lean/corner anywhere near as much as I could. It gets especially bad on switchbacks picking up speed where you essentially have to increase the amount your cornering as you pick up speed exiting. It will improve with continued practice and especially as I start doing more rides trying to keep up with other riders and being able to watch and learn what lines are possible at what speeds.