1st. The negatives look great, I firmly believe that if you print those negs in an enalrger you'll see a LOT less grain.
2nd. Cheap coffee works fine, it is the caffeic acid that does the trick. And robusta seems to have more of caffeic acid and less of those flavour dingies.
3. FWIW I think Folgernol/Caffenol works best if you prepare it with the washing soda first (until all the grit is gone), then the vitamin C, then the coffee. Froth is gone, and you neutralize the caffeic acid faster thus releasing the cathecol-like chemicals.
Adding vitamin C was my idea to minimize the stain in Agfa APX400 which made the negatives unscanable but allowed to be printed in an enlarger. The stain is almost gone (depending on the film) but also the shadows get a small boost.
You did say that is TriX, do you have another Tri-X negative scanned, that should be a firer comparison
I tried it in several films and like other developers this one is a "honest grain"one and will only show whatever structure your film has.