From what I understand he is derived from the Mayan Mam, so yes.

Not quite; it's a mayan folk saint in Guatemala more commonly known as Maximón, and the painting is of one of his shrines.

free software, i use it for the computer but im sure it exists for mobile aswell

I am unfortunately bad at communicating with any medium other than art, but I recommend the book "The Cultural Evolution of Ancient Nahua Civilizations: The Pipil-Nicarao of Central America", that or more simply; Wikipedia.

Most of the body is covered with black paint, the ingredients of which I do not know but id guess charcoal/soot.
The legs however are tattoos, the designs of which are based on Nicoyan pottery figures. Unfortunately the Nicoyan figures are the best guess I got on what design might have been worn.

Medibang with mainly the G-Pen brush

Oh my goodness 🥺

The backyard birds. Once I varnished and find nice threads for them all I'll make a better photo of them all together:)