parametric optimization will let you optimize towards a specific value but won't let you maximize/minimize a function like you're looking for. your best bet would be to use a parmetric sweep to go through several speeds and then look at the results to see where your maximum is.
net torque would be the same method as you have for force. pick a location, pick all faces, and then use a goal to output torque.
highly recommend you start with a 2d simulation of a 2d wing profile to get your method down before you go to 3d. lots of forum posts about how much mesh, size of comp domain, setting up force and torque goals to study before you get starte.d