After printing a few of these I have some suggestions.
1: add holes to the bottoms of the molds to allow air in.
2: increase one screw hole size to accomodate an M4 screw. This will allow one handle to spin freely while the M4 screw is firmly threaded into the other handle.
3: use a release agent like candlewax in the molds after printing and the snowballs will fall right out. If they break apart, pack more snow in!