Archer only survives because his ability is interrupted, if it wasn't then he would die. So I would suggest that Ahimelek will flip over during battle resolution.
Interesting thought, and while it starts correct, I would disagree with the conclusion.
Archer is not the same type of ability: it is designed to trigger
after the battle, and as such is not treated the same as something that is pending but not yet had a chance to activate. The reason he survives is because the interrupt
makes him pending, and thus it cannot reactivate, and you are correct that he would die if an EtB is used because his ability is designated to trigger after the battle ends already.
However, that does not mean that
this ability is treated the same way. Ambush is designed to trigger "on block," just like other abilities trigger "on draw" or "on search." Once the blocker is presented, it is then
pending, waiting for its chance to activate. However, if the battle ends, it is still pending and thus does not get to actually activate. He does not flip at all.
The phrase "When opponent presents an Evil Character in battle, Hero is flipped face up" does not mean "the next time it is blocked" but really "whenever it is blocked," and so it would be able to flip in a future battle.