From what I've read here, changing the ability points in the xml doesn't actually change the amount you get for some reason. But over in the my documents folder area where the save games go, there's a file called something like CustomRacesConfig or something (sorry I can't check it now) that you can edit to whatever you want for the starting race stats, so you can figure out what you'd get with the allotted ability point amount and just set those as starting values directly.
Then, when you start a game, just accept those values and don't modify them any further on the race setup screen.
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