I managed to work around #1 by creating a secondary sheet that QUERYs only the immutable columns.
This approach only works if you don’t need any mutable values in the rest of the flow, usually I’m not so lucky 
In theory you could bring in the mutable values with “Find Row” on the primary sheet, but then you’d effectively need to manually implement the “identity key” mechanism I’ve been discussing with @abuaboud.
However, because these pieces work with row numbers this’d leave the door wide open to lots of fun race condition shenanigans.