I might get crucified for this, but what the heck. It's how I feel.
Abe is my age. I have a great many Jewish friends who are his age. My ex-husband, who is Jewish, is his age. I live and work with many, many Jewish men who are Abe's age. Not of one of them speaks like Abe.
My problem with Abe is this: he does not sound like a single, solitary Jewish person of my age. If he were 20 or 30 years older, his Yiddishisms would be more appropriate. From what I understand, Abe was born and raised in New York. As he is written, I think Abe is an anachronism, more of a caricature than a true character. Abe is the sole character in the RJ series who does not ring 100% true for me.
Every Jew I know uses Yiddishisms here and there. I do, too, as do many New Yorkers, Jewish or not. But no one I know who is his age speaks like Abe. Older New Yorkers do; some of the older parents or grandparents of my Jewish friends may sound like Abe.
I love Abe's heart and the man that he is. I love how he fits into Jack's life. But Abe is not real for me.
I've turned a few Jewish friends on to the RJ series. They like the books, but to a person, they are uncomfortable with Abe and find the way he is written to be a detraction from the series.