Iirc 2017 was the last time it was stocked. Yes they do over-winter, or at least some have in the past, but they do not spawn as there is no outflow creek in the fall. Hard to say how many are left at any given point.
The other thing about that lake is they are picky like no other brookies I’ve ever seen. There is one size/color fly that I found works and I had to hike up there three times to figure it out
in hindsight I could have caught a lot more fish for a lot less effort somewhere else, but it was a fun challenge