Does anybody know with the sherman tanks, if the engine has to be running in order to move the turret?
No. There was an electro - hydraulic system allowing the turret to move using the battery and a generator. in case of SHTF, there was also a crank... I used to play in a derelict M4 as a kid, and the crank worked well even if the rest was heavily rusted.
"The French soldiers are grand. They are grand. There is no other word to express it." - Arthur Conan Doyle, A visit to three fronts (1916)