Along with training the short, high power efforts, work on technique.
I'm 9 years older, 174 kg, and way lower in FTP and 100km or 100 mile times. GC says my 10 second max is around 650, 3 seconds around 750. (I expect that 3 second or shorter power numbers can be somewhat inaccurate, I hit 700-800 quite easily by just doing a couple of standing hard pedal strokes, like at the top of a moderate downhill to get my speed going. It's mostly body weight.)
This recent
NorCal aero vs power video is interesting. Jeff is way up there in sprint power, but the ideas apply to the rest of us. It discusses the difference between optimal aero and a less aero optimal power posture. So I googled "road bike optimal position for short sprint power", and liked this Trainer Road page on
Cycling Sprint Technique. And that page has a link to
Cycling Sprint Workouts. (My impression of Trainer Road is that they like to make things complicated and quite technical. They do want riders to sign up for their paid programs, of course. Still interesting to read.)
Work on standing, pulling hard on the bars in the drops at an efficient angle, and spinning up the cadence without losing power.
When I used to ride a fixed gear occasionally years ago, it made it obvious when my fast spinning timing was off. If the wheel was turning, so were the cranks, so any bad technique was instantly obvious. If I was still pushing down on the pedal when it was starting to rise back up after the bottom of the stroke, I'd bounce right off the saddle as the cranks were rising while I was still pushing down. With road bike freewheels, all this does is waste power fighting the opposite leg, there's no bouncing feedback. It did help with smoothing out my high cadence, and boosted my efficiency a lot.