Hi - I don't have answers for you, but some similar situations and thoughts.
First, I've checked somewhat into the family Boris and Hasya/Chasie/Jessie (Krainin) BOBRUSKY/Bobruskin in NY - because their photos showed up among the very few photos that my grandparents (from Gomel and Cherikov) had. I find that Fannie KREININ married a Samuel DINKIN in 1915. But these are New York folk, so maybe/maybe not related to your Harry DINKIN.
Rather than start combing through all that material right now - let me know if you have any interest.
The other thing is that my own paternal GF was said to be joining a "Brother-in-Law" in Philly - also "Cousin" is written in, I've studied that family (who did live next to my gp's in 1910 ONLY), including corresponding with descendants - so far we can find no relationship. Both men were from around Gomel (so was Bobrusky) so they may well have known each other.
I wish you luck - your query sounded so similar to mine that I needed to reply!
Best, Martha