So maybe if damage was cut in half, and maybe something simple and universal like all ingredient drops are doubled?
(like if the game usually spawns one leaf, it would instead spawn two?)
Maybe health drops would heal slightly more as well?
Hmm, looking bad at it, I think I didn't take the most damage by being hit too hard, but by being hit too often.
Prime example probably King Jelly (although it isn't even shooting). My first few battles with him, I was basically being hit constantly.
And the many homing shots in the game. Like the second form of the last boss. I somehow had a hard time dodging the poisonous projectiles, although they were pretty slow. And once these just hit you once, you already are more busy keeping yourself alive and the poison off.
So, I'd really suggest to decrease the number of projectiles the enemies shoot. Maybe make them slower, or have them reach less far. Sometimes I felt a projectile was chasing me through a whole map xD
Staying with the King Jelly example, I would make him spawn less critters (or make these easier to kill) and have him rotate his beams more slowly and maybe less abrupt.
But yes, all in all, decreasing the damage and increasing ingrident spawning/healing would already lower the difficulty by a BIG amount. Maybe even spawn less ingredients and more "assembled" healing items. I was always having a big deal of ingridients, but in the end, there was just too much stuff I could create with it, of which in most cases I didn't even have an idea what they actually do (as the recipes don't show the effects).
So, I mostly just ended up doing the most basic healing items. Like Leaf/Healing Polutice and maybe a Tough Cake.