This has probably been asked in this thread, but..
Do normal 32bit apps, with no '64bit' support such as Firefox, Unison etc work when in the full 64bit kernel?
Yes.
32 bit Kernel works with 32 bit and 64 bit applications. 64 bit apps can still use over 4GB ram.
32 bit Kernel only works with 32 bit kernel extensions (kext).
64 bit Kernel works with 32 bit and 64 bit applications.
64 bit Kernel only works with 64 bit kernel extensions (kext).