I realize this resembles a one man show, but so be it.
Problem with micro sd card - after full format in Tascam - solved.
Problem with .dff playback in Foobar - not solved. It insists on playing them as pcm, whatever components and outputs I try (foo_this, foo_that). While .dsf files play fine, as 'true' dsd. Maybe in some systems it doesn't matter, but in my case, the true dsd playback (where volume is disabled) is truly worth it.
Happily, Audirvana plays both .dff and .dsf just fine. I also wonder if it plays the .dsf files a bit better than Foobar. Slightly more sonic space, and no breaks/gaps like I sometimes think I hear in Foobar (maybe, a buffer problem). Not sure, though.
Testing recently recorded LPs like Beatles: Magical mystery tour, the German Horzu version with true stereo. If you have rare costly LPs like this you owe it to yourself to record them to DSD. And the better the sound of the original LP the better it is from the DSD file.
It can be subtle, though. In this and many other cases, the streaming version of the album (on Qobuz) is not actually the original. It is "remastered 2009" whatever that means. They have obviously tried to fix the sonic problems of the original. Superficially, for a short while, it sounds better. In the longer run, no.