There are several things I enjoyed much. That is the constant groove and the almost on all places very good tight rhythm connection between you both. I could imagine the vivace movement to be performed more lively, and I would not expect problems from your piano playing side. However since the intonation seems more difficult in faster viola passages it is better to not play faster here.
Your piano trills are very good, fast and evenly!
Why this Bach only as warming up? I can imagine that you prefer the Brahms sonatas because of more work for piano, but overall seen I think you both sound very well here on Bach from the musical side. Also regarding viola playing, I enjoyed almost more as on Brahms. Can't really explain, maybe on baroque pieces the strong side of your duo, the rhythm, is of advantage while romantique pieces like the Brahms is more sensitive towards pitch issues.
Maybe, to enhance the groove more like the modern style of baroque interpretations, is you could both check to put the accents more on the main beats. You do so on piano, could be stronger to my taste, and for Alex even much stronger. It is only so that I watched a very good baroque orchestra from Hanover, they play with much groove and accents and almost without vibrato because this was not invented for string instruments in the baroque time. That sounded very convincing to me. However, without vibrato is even much, much more difficult as with, because the pitch must fit 100% otherwise better with vibrato.
I agree that from recording side, the piano should be louder. If you could afford two separate mics to have separate channels for viola and piano and mix afterwards together, it would be sound more professional from recording quality. Is worth the effort.
They have two puppies that are sort of in puberty now and really irritating (though very sweet). Of course they picked this moment to throw a paddy - the little shits. I was glad they kept quiet during the Brahms.
No, they did not throw a paddy. That is the dog style to spent applause, the first woof was after a very good long piano trill.