I think it's a big problem that you translate judia as Jewish and miserly and tightfisted - that is crossing a line
I agree it's unfortunate, but it's accurate. The word does mean Jewish, but it also has those other colloquial meanings, and to ignore them would be bad teaching. If you were translating from Spanish to English and came across judío where the author had used it to mean miserly and you translated it as Jewish, your translation would be incorrect. (e.g. Ebeneezer Scrooge was a miserly man. He was not Jewish.) On the other hand, when you're translating from English to Spanish there are alternatives that are not so offensive, and I would hope that we will learn them here.