Den.Sea Mary'Snow King'

[NYCorchidman]

No, don't risk damaging your plants by putting them outside where it goes below freezing.

8-12C is cool enough to flower any varieties.
Plus, your cultural description seem very good except I am concerned that you reduce watering too early.
As long as you keep the canes plump, all is well.

I'm surprised that most of the leaves are still on under 8-12 C. Mine used to shed all the leaves at around & under 10.
Now they shed either none or a couple lower leaves in the fall. I usually strip them all off. They get in the way and I can't see the few flowers I get. lol

Light???

Anyways, with 8-12C, it is natural that they won't flower but wait until the temperature warms up a little more.

Mine ( when I had them under 10C) would start showing buds late January into February, and then flowers opened in February into May.