Wow thanks so much for trying the new version and for writing all of this up! (I apologize in advance for the wall of text I'm about to respond with).
The wave fights: Thanks for this feedback, I think I needed to hear this. Looking back I think the wave style is a tiny bit lazy on my part: I want to test the player with a certain set of enemies in different configurations, and waves seemed like a good way to do that, but in retrospect I think the best fights in the game are the unique ones that are only 1 or 2 waves total, followed by a non-combat section (like the first and last parts of dream 3). I think it helps keep the game more fresh and varied, so I'll definitely look to find better ways of testing the player instead of just spamming multiple waves.
On combat options (reflect vs attack): Before I give my rationale, I want to say that I totally hear you on it being a little unclear what "weapon" to use for a given fight. I think the wave-fights / design of having tons of enemies on screen is a bit to blame for that (too many enemies onscreen = tough to judge what tools to use). That said, I think one of the best parts of the game is being able to deflect while attacking, so managing all the threats on the screen at once while hitting something was something my friends said was really satisfying.
My philosophy for attacks and reflect timings: There are two types of attacks: Projectiles (the reflect timing is dictated on visually judging where the projectile is relative to you), and "double-cue" attacks (reflect timing is denoted by two visual or audio cues followed by an attack, i.e the laser, the explosions, etc). My intention was that these two would hopefully be able to tell the player when to reflect, but again I totally feel you in that it can be unclear sometimes. Making these cues more telegraphed is definitely a good idea, thanks again for mentioning this. I'm wondering if there's a world where I can make the reflect window a little more generous without trivializing the encounters.
The music: Sorry you didn't like the new music! Myself and my playtesters actually really like the new music, so I think it's just a personal preference thing (I've played Celeste and the music is incredible in that game, but I don't think that style would suit this game). That said, I'm willing to agree to disagree here, thanks for giving feedback on it anyway! There's always more tweaking I can do.
New content: Glad you liked the new enemies and secret boss! Also, holy crap I don't think I know many people (who don't know me in-person) that have played Jingnon's Ascent! (Also shhhhh don't tell anyone I'm reusing assets haha)
Misc: (Screen fade bug) good catch! I think I just didn't scale the black panel on the screen fully. I can fix that pretty easily. (Save/load functionality) Ahhhh this is coming, sorry I've been prioritizing a lot of other stuff. The "dream select" menu is a temporary workaround for the lack of save/load, but it's definitely coming soon.
The assist modes: Yeah these are tough to get right, I'm pretty new to assist modes and they're always a little scary to implement. I've seen GMTK's video on Celeste's assist modes, which is where I got some of the ideas from, but I'm still on the market for more options for players. Which assist modes did you find yourself using? Also, if you don't mind me asking, what about them felt intrusive? Was it the fact that they were kind of "in your face" as soon as you press pause? (If so, that's only temporary). I'm planning on putting them behind a bunch of dialogs like Celeste (so that the player understands that the game was NOT balanced around them).
Thanks again for playing! You have no idea how much I appreciate detailed writeups like yours,. It's really tough to get honest feedback from people, so thanks so much!