Since this model has no case screws, what holds the movement in the case? Also, is the tadpole regulator adjusted by the tiny screw seen on the regulator?

The '72 model Waltham is held in the case by the stem on one side and one case screw on the pillar-plate, near the balance cock.

There is no screw regulation - the tadpole pointer is pushed to where you want it, but the eccentric bulb on the tadpole moves the regulator itself in a more controlled fashion. It works the same with either cam regulator. The screw just hold the cam in place.