Because you cant push a launcher or get into any settings menu, my only suggestion would be to flash a new rom. And assuming that the rom you just flashed (being completely stock), you wont have the 3 button combo although I suggest you try it. (Im not sure about the combos for 2.2 roms).
If you cant get into recovery/download through any method, my next suggestion is to buy/build a JIG and force your device into download mode, by which you can use ODIN to flash a rom.
You can make a jig for about a dollar or buy one for about 10. (Best purchase i made). Just take a look around the forums for more info on this.