Ok, so latest "official" version for FM3 series is 03.10.02.Rev.00, but for all FMB series i guess we could say its 03.10.08.Rev.00.
Also - if i were you - i would not look too much into "errata sheet" for various "stability improvements" -> because these usually mean various bug fixes done on FW.
But those bug fixes - might have have been targeted NOT for FM3 devices at all. I.e. maybe they were targeted for FMB1 or FMB0 series devices.
So basically - if current FW which you have - is working for you - i would not look for newer versions and use what you have.
Unless ofcourse you are having problems with current FW - then it a correct action to seek new FW.
Or you know for a fact (from errata sheet) for example that newer FW versions - have new features which you want.
Anyway FW 03.10.08.Rev.00 can be retrieved at:
Additional info - newest "experimental" version is 03.18.xx / 03.21.xx depending on various development branches. In the near future like 1-2 months (maybe sooner) - most FW versions should be updated to 03.18.xx. But like i said - if what you have works - and you are happy with features present - there is no point in seeking "newest fw" versions.