1. Here I would do something like this:

  log("deducting credit...", DeductCreditInRatingGroup),

  ...

  log(Msg, true) -> do_the_logging();
  log(Msg, false) -> ok.

Nowadays though, you should really use the new logger introduced in Erlang 21. There you can do run-time filtering on many different parameters, or even write your own handlers. Using if-statements is usually considered an anti-pattern in Erlang, and I think very common coming from languages where only if-statements exist. Problems are almost always better solved by using case, or even better, pattern matching in function heads.

2. Sounds like one of the rare cases where you care about the error and can also handle it. In the use case you mentioned, I would buffer the data outside of the loop that produces it and wrap the loop in a try-catch statement. That way, you don't loose the data if one iteration crashes.

4. Erlang usually ends up being good at latency and concurrency (scalability over cores), together with a smaller and easier to read code base. I'm curious about your case, and what would have made Java a better fit. If you share a lot of global objects, Java might be faster for some things (at the cost of concurrency usually). Erlang has tools for that as well though (e.g. ETS and recently persistent_term).