Im originally from "Southie", (South Boston Irish), myself...lol...Then was in NH for 20 years until 10 years ago and im now in New Mexico, retired, these last ten years...lol...DAMIEN
Make doubly sure that your rear wheel is perfectly "trued"...make sure that rag joint and sprocket are also not wobbly at all when you spin it...That last chain pic looks like there is a definite curve in it from misalignment...DAMIEN