1.
Light dimmers aren't likely to work with smart film. The inexpensive triac kind are intended for incandescent bulbs. Modern compact fluorescent bulbs need a modern different kind of light dimmer. Further research might turn up a dimmer that works with smart film.
2.
An autotransformer is versatile since you can dial in any AC voltage from zero to house voltage plus ten percent. (I paid $10 for a used 1.75 Ampere unit on Ebay.) With your current draw being a few mA, an autoformer is more than adequate.
3.
Two inexpensive wall wart transformers in a row. The first steps down, the second is backwards at a lesser ratio than the first.
Say, 120 VAC to 9 VAC @ 300mA. Then a second one designed to step down 120 VAC to 15 VAC, installed in reverse. The resulting output is 75 VAC, usable for smart film.