Thank you so much for playing!! The secret boss is a lot harder than the rest of the game, but i believe you can do it!! Using the dash can certainly help, and it's a matter of getting to know their patterns. I'll take note of the items and the money, and I'll hopefully find a nicer and more understandable way to implement them! All in all, I'm really happy you enjoyed it... it really warmed my heart to see such a detailed review!
I came back and beat that boss (sorta). I went to the shop and stocked up on 30 healing items, making the boss an absolute cake walk. The boss was doing all of this crazy stuff, but I had an endless supply of healing items. tbh, it kinda cheapened the boss, and you might want to put some cap on how many healing items you can hold. The 30 healing items weren't even that expensive.