How does it do versus the default Workshop/Gardens included with the simulator?
Obvious change - it shouldn't always take silver over estate! As it is, this bot will buy up a bunch of woodcutters, then run out the gardens and woodcutters, and then build up enough silvers to run out the duchies. As it is, with $4, I think in this rush, Estate/Estate is better than Silver/Copper when Gardens and Woodcutters run out.
Things you may want to try optimizing:
1) Play around with the number of Woodcutters to get before gardens. You pointed that out yourself.
2) Buying estates should probably take precedence over buying silvers? You will be buying things with mostly woodcutters and coppers, I suspect that by the time the woodcutters are out, you want estates rather than silvers? But you should sim that and see whether it's actually true.