That sucks, sorry to hear. I do appreciate you and the others posting their experience, I had no idea Subaru had this poor design on some of their AC systems.
I wonder if it is the variable displacement valve that is toast and the compressor repairable?
Since it can build up pressure but cant hold it, it could be the variable portion malfunctioning, which I've seen repaired in other model compressors by replacing the variable displacement valve.
I doubt it is available as a separate part from the dealer though, but for some compressors you can find them online.
However with the clutchless design another failure could take out more of the system so you may be better off getting new.