> When do you thing the 2.5 RC3 will be available ?

Soon, i hope before the end of May

You can try snapshot build, it was refreshed today:
http://www.firebirdsql.org/download/snapshot_builds/win/2.5/

Note, it contains fix for "your" bug with monitoring CORE-2993:
http://tracker.firebirdsql.org/browse/CORE-2993

so, i highly recommend you to try it and report back your expirience.
It also will have impact on when RC3 will be released.

Regards,
Vlad