Hi!
Some years ago I decided to play the first game and saw that it didn't have damage, hit, number of attacks info before the attack. These days I started studying a little bit of VueJS and decided to make an calculator for it.
https://bertuga.github.io/fire-emblem-nes-calculator/
More details about it here: https://github.com/Bertuga/fire-emblem-nes-calculator
It's not that practical for use as you play, but at least is something. It has the calculator for the arena adversary too, some entries had two possibilities, so if any of you tests it in-game and could tell me which one really appears, I can fix it.
Any feedback is appreciated, I hope it helps you guys some way, like trying to exploit the arena.