I just compared some the results of that calculator with our old one, and I guess if that one is right then everyone who ever sent us feedback about ours being wrong is an idiot.
Because our old max hit calculator that was removed due to it being incorrect supposedly, but it gives the exact same result as that one you have given for all the numbers i have tried.
If that calculator that you gave a link to is correct, then we don't need it, and we don't need to work on a new one.
The only thing we would need to add to ours is the special attacks, which can easily be done with a little research.
Here is the link to our old one, it has always been there, we just removed the link to it.