Slitherine

When a commander comes in front combat with a BG of mixed HF/shootingLF, MF/shootingLF HForMF/shooting MF he upgrades the quality of the combat dices. What about the shooting dices from the rear ranks during impact? Are they upgraded too?

Yes

The dice resulting from support shooting are not 'shooting dice' they are a form of close combat dice but they use shooting POAs and to hit numbers