So what was the problem? It is important to explain what was wrong on your side to help others that can face the same problem.
I could not see why filtering by service reference is needed. We can all dream of nice to have but we need some concrete user case to show when it is useful.
log size is limited because log is stored into memory, it is only written to disk when you select save. And some end-users with cheap or end-of-life STB are really limited in memory so the current size is a compromise and nobody is going to read everyday the EPGimport log so there is no real needs to have it written on disk at every run.