Thanks for playing. I think this is the best in the series as well, glad you enjoyed it.
The final boss fight wasn't supposed to be that hard, there are multiple ways to deal with the boss's seemingly unfair attacks. Crown of Thorns reflects all physical damage, and you can also deal with the telegraphed attacks by guarding and lowering the boss's ATK. There's also other defensive options like Shield of Valor, Hexproof Chant, etc. Also there are items to buff or debuff units if you don't have access to buff or debuff skills for some reason.
This is actually RPG Maker MZ. I could have used the leveling plugin but for some reason I thought I didn't need it. I should have used it after all. I didn't think it was too annoying because I didn't use the knife that often