It's been awhile since feedback and I assume you aren't looking anymore and this may be against your vision but I will say my piece: Adaptive difficulty does not belong in this genre.
When I replayed the fight against Violette and realized her attacks change depending on if you've been hit, I immediately had three thoughts:
1. Whoa, sudden difficulty spike
2. Aw hell, I missed content
3. I played a lesser version of the fight and feel patronized
I'd much rather there have just been a normal, easy, hard, etc like in other games. Not only does the way this adaptive difficulty is handled feel a bit confusing but it also makes practice feel pointless. If I practice a whole stage and get hit once, then practice again no-hit, then I am suddenly no longer practicing the same stage. Makes the usage of a hit-points system kinda pointless since now I'm inclined to slam reset at the slightest bit of damage where I might otherwise press on. If all of this is the intention and part of the vision for the game then by all means go for it but feeling constantly anxious that one hit of damage instantly means I'm playing lesser of a game than others is not my idea of a good time for a shmup.