Ladyfish,
If your bcd was self inflating, the thing to have done is disconnect the inflator hose. If for some reason this cannot be done immediately, hold the deflate button fully open while holding it HIGHER than the bcd, until the hose can be disconnected. Most deflators (I don't know about the Air-2) are designed so that they can vent air faster than the inflator can flow air into the bcd.
I have dived Dutch Springs, both with a Conshelf and a Mares MR-12 (essentially the same first stage) and the deep hole is pretty cold. But, even though a Conshelf is a diaphragm first stage, and is normally reliable at 40ish temps, the constant flow into your bcd likely caused it to freeze which was responsible your second stage freeflow. You tried your best to slow the ascent, which is commendable, but a rocket ride to the surface can be extremely dangerous.