[Radek]

I have no experience with Mac. You could be right. At least some hints:
1. The patch files are pure text files. Does the Mac accept them or does it need some headers or so? If it needs then try to convert the .2DA files into the "Mac" pure text.
2. What exactly do you have? A single xpcap.2da file or level 50 rules? The xpcap.2da alone cannot help you. Well, you'll be able to gain levels but you get almost no benefit from them. Only the automatic benefit, like increasing Turn Undead level and, perhaps, HP. No additional proficiences, no improvement in saving throws or THAC0 and so on.
3. The xp cap remover reveals itself when you reach next level. It does not modify your current state immediately. Until then, the only sign of presence of the xp cap remover is your gaining XP again.
4. Is Mac case sensitive? If it is then try to convert the filenames to lowercase and uppercase or, better, catch a binary editor and look at the game .exe files. The names of the patch files should be stored there somewhere and they should be stored in the wanted form. Perhaps, without extension. Try both .2da and .2DA .
5. It is also possible that the Mac version of SoA uses another mechanism of patching. In this case, you can delete the files from your machine. But I don't believe that. Why?