Try a factory reset. You can backup and restore with Kies. I have read literally hundreds of posts where the poor battery life was solved following a software reset.
I don't know why manufacturers don't make it a *requirement* to perform a wipe when updating software to a new major version.
Philips AS351/05 Android Speaker Dock
Not cheap but they do exist :p
You may be able to find something better/cheaper, I don't know.
Personally I just bought a bluetooth speaker which I can use with my iPad too. Then you can just stream your music over bluetooth whilst it's sat in a...
Samsung Galaxy S2 Firmware Updates via Kies Official Releases compiled list ~ Android ROMS
Considering the build date was September 2011, it's probably Crotia according to that site. Did you buy your phone off an individual rather than from a store?
I own an iPad and the Apple wireless keyboard works with the SGS2 also. None of the function keys do anything, but arrow keys, tab, return and all of the letters/numbers work fine. :)