I don’t know what dialect you speak where “Mano” is masculine. In Spain it is feminine, and I’ve never heard anyone say “el mano”. I’ve also never heard anyone say “el manita”.

I don’t think “ser” and “estar” being different verbs is at all wrong with spanish. They are very clearly different concepts.

You can be something because it is part of you “I am tall” or you can be something situationally “I am at the library”. What is weird to me is that English uses the same verb for those clearly different concepts.