Hi, and thanks for the response.
I can see your point about hardware approaches to the problem, but I’m not in that league :).
Also, GPSDO is not an option until I can afford to upgrade from my RSP1A.
My reason for trying to measure MW offsets is that they are often characteristic for a particular station and can therefore help identification when audio is not conclusive (this is a MW DXers specialist interest).
As for the other parts to my question, these are to clear up doubts how RSP/SDRuno operate and whether there are any problems here.
Happy New Year.