I haven't been able to get applehda working, only voodoo. I did a lot of research about patching applehda but I couldn't wrap my head around it and kept running into roadblocks. I can use the volume keys, but f keys aren't working. If I change the settings for the elan touchpad kext I can get f keys working but then volume keys etc don't work.
Could you upload your PS2 kext to me? As I couldn't get my friend's X202e work with two finger scrolling, I'd would to use your PS2 kext settings.
Regarding about FN keys, try to add "Name (OSDW, 0x80)" or "Name (OSDW, 0x100)" in your DSDT:
OperationRegion (DBGM, SystemMemory, 0x000D0000, 0x04)
Field (DBGM, DWordAcc, NoLock, Preserve)
Name (OSFG, Zero)
Name (OS9X, One)
Name (OS98, 0x02)
Name (OSME, 0x04)
Name (OS2K, 0x08)
Name (OSXP, 0x10)
Name (OSEG, 0x20)
Name (OSVT, 0x40)
Name (OSW7, 0x80)
Name (OSW8, 0x0100)
Name (OSDW, 0x80)
I don't have the machine with me, so I can't test if it works. Hope it helps!