Really appreciate you playing the game! Bonuses to next attack work :), the explanations are just a bit bad. They impact the attack of the current turn. The game does have a bunch of bugs we unfortunately didn't have time to fix, so hopefully it didn't ruin your experience. What you got to was indeed the ending, so no worries there. Thanks a shit ton for the feedback!
(When leveling up, attack bonuses increase your likelihood to hit the enemy, not the damage. Damage bonuses increase damage, but I agree that's very confusing, our bad :). )