Question

What is the temperature on the farenhite scale at which all the molecular motion nearly stops?

Answer 1

That would be the temperature of absolute zero, 0 K or, in Fahrenheit, negative 459.67 F.
At this temperature the constant oscillation of atoms in molecules ceases. This temperature can not, in reality, be reached. Furthermore, even if we did manage to do that, if we wanted to observe such matter we would necessarily have to interact with it increasing its temperature, so for all practical purposes, this is purely just an exercise in pure theory.
Note, though, that even at 0 K there will still be some energy left in the vibrational modes, the zero point energy.