Your bathroom sounds ideal for the phalaenopsis. If you want to measure the light levels exactly see
Measuring light levels with an SLR camera
Phalaenopsis need about 150 foot candles of light.
If the light was too high you would already have had problems. The leaves fould burn (Chlorophyll dies and turns brown). Short of burning the more light you can give an orchid the better. They probably can go almost up to the frosted window.
Cleaning the leaves is fine A little water cleans them easy and a little oil shines them well. Oil sprays are used on plants to prevent many insects. This is not an issue inside but since it is harmless to the plant you might like the shine. (It is a common trick to make plants look better for competition shows)