Wow, this is painted at an extremely high standard Gustavo! The colours, tones, transitions, NMM on the metal post...it's all spot on and it very much looks like a classical painting!
As you are such an expert that I am almost embarrassed to comment, but please allow me one nitty-gritty comment: I don't think the dark line at the bottom of the Madonna's eyes is very realistic. There should not be a shade there. The eyes of the (famous) baby boy don't have that line and look more realistic.....in my humble opinion....
But wow, what painting! Just great.
Cheers,
Adrian