I've never found such data.
Your best guess would be to search for this code in the .exe or .dll files because I think it's hard-coded ;-)
If you want to change that, it should be no problem with some Osiris scripting.
- the event CharacterLeveledUp((CHARACTER)_Character)
- possibly the query CharacterGetLevel([in](CHARACTER)_Character, [out](INTEGER)_Level)
- the call CharacterAddAttributePoint((CHARACTER)_Character, (INTEGER)_Amount)
- the call CharacterAddAbilityPoint((CHARACTER)_Character, (INTEGER)_Amount)
- the call CharacterAddTalentPoint((CHARACTER)_Character, (INTEGER)_Amount)
- 'The Divinity Engine Enhanced Edition' to compile your script
... and a tiny bit of knowledge about Osiris and its 'databases' ;-)
It could be that the _Amount variable does not work with values other than -1 and +1, so adding more than one could require some additional steps. At least I remember that I had to do something like a recursion or a loop to lift the Loremaster ability up to 5 in my XC_Bags mod. But how each of the calls works in detail is subject to testing since we have no documentation ;-)
PS: the names of the calls come from the file Mods\<mymodname>\Story\story.div', a file that is auto-created by the Osiris compiler when it runs, I did not test the calls/event myself ;-)