It took forever but I think I found it.
Based on Good Reads, it is the The Tsaddik of the Seven Wonders by Isidore Haiblum.
- I read it mid 80's. Published 1971.
- The story is about an investigator working for a government agency regulating technology or some such. It's regulating time travel.
- He also had an alien monkey sidekick IIRC. Something of an ace in the hole. This is Greenberg the homunculus.
- Lots of Jewish, Yiddish phrases including Sitra Achra. It's a funny novel, filled with jokes and humor. The reviews mention it's full of kooky humor.