wears out the hub faster too

the rocking motion induced by going from one direction to the other when you skid causes the spokes to wear the hub faster by making them wear grooves into the spoke holes unless you've got a hub with straight pull spokes

As for lower gearing like with a mtb torque is multiplied by gearing while power is divided so yes you can easily using mechanical advantage of gearing generate more force or torque at the hub with lower gears although with much less power. Difference with a fixed gear though is the sudden change of direction of the power, you tend to go from full power one way to the other causing sudden stress on the hubs and spokes and rim.

I've worn out two hubs so far from riding fixed, both cracked thru the hub flange at a spoke hole.

horsepower = (torque * rpm)/5250 where torque is measured in foot-pounds........and humans are similar power wise to electric motors with max torque at or close to 0 rpm and max power closer to max rpm. Not hard to plug in some numbers in that equation and work it out even with the multiplication of torque or division of torque created by gearing. My powertap readouts as do most I would think will give you charts of torque and power measured in watts and it varies from 5-10 ft-lbs cruising along to up around 300 ft-lbs from a dead stop depending on gearing. But that is measured at the hub, at the cranks the torq is divided while hp is multiplied due to gearing having the cranks spin slower than the hub. On a mtb where you can have the cranks spinning slower than the hub the difference swings the other way where at the cranks the hp is divided and the torque is multiplied in relation to the hub.