NH3 only acts as a reducer for the Na/Li to produce a metal/ammonia solution containing the solvated electrons which reduce your pseudo to meth.
Although a minimum ammount of NH3 is required to dissolve the metal, Swio has experimented with excess ammounts of NH3 with no real variation in results, providing the correct molar ratio of pseudo/metal is used.
Therefore i can't see how replacing NH3 with anything else would vary the quality of ur goods.
As for replacing NH3 with chlorodifluoromethane, i'm not too sure if it's possible. Maybee one of he smarter bee's can help you out there.
Dissolving metal reductions are very dangerous and i would make sure i was certain about variations before attempting them.
cheers