The motor getting hot isn't unsurprising since every time it changes direction that apruptly, there will be a huge current spike.
But I am somewhat certain these motors have an overheat protection build in.
So as long as it doesn't abort a cycle with an error I wouldn't worry.
And I might be mistaken, but on VMWs, the transmission is a planetary gear set.
From what I understand from the bit of technical information about the gearing setup, and the bit I learned about that type of transmission in uni, keeping the agitator stationary with very little force seems reasonable.
All torque you put up will just mean more torque is directed into the tub.
The agitator is only connected indirectly to the drive at any time. It's basically connected to a seperate center gear to the input gear - same specs, just not physically connected to the input, only via the planetary gear set.
The tub is connected to the planetary gear carrier.
All torque goes through there.
Stopping the agitator by hand just means all torque is going to the tub.