Agree, I am just talking from the perspective of someone new to comics, Magneto being jewish would not be apparent considering the 90`s retcon and storylines like House of M in which Magnus is considered his name. So to explain all that, it`s neccesary to point to the original work of Claremont about the character, the retcon issue, and Magneto Testament. Just my oppinion.
2.- Even if he were to be considered Sinte, he still would be an Holocaust survivor. Magneto Testament did make that very clear telling Magda´s story. I would like if some writers in the future, maybe Pak himself if he decides to write the sequel of Magneto Testament, to really get into Magda´s head and get to know her better.