I get the Forest Hills argument. At the same time, coincidences like that are common. I have an Italian-sounding name and grew up in an Italian-dominated area, but no one in my family is Italian.
I think the problem with 616 Peter being canonically Jewish is:
1. It ignores Stan's wishes and sense of identity. We know from Riesman's biography that Stan didn't have a sense of Jewish identity and saw himself as just an American / New Yorker.
2. It reinforces Marvel's downplay of Ditko. You know, the idea that Stan is the primary creator of Spider-Man and not Ditko (who wasn't Jewish). I'm not one of those "Stan didn't create anything" guys, but it's clear his input was secondary compared to Kirby and Ditko.
Not sure about MJ, but I don't think there is evidence of her being intended to be Jewish either.