Didn't find where it says any of that, but since it's based on OGL which is based on D&D, I know off hand the answers:
a) You gain 1 new ability point every 4 levels, that is to say 4, 8, 12, 16, 20.
b) The exp you need for each level is:
2 = 1000
3 = 3000
4 = 6000
5 = 10000
... etc.
You add the EXP needed for the current level(for example for 4 it's 6000.), then you add 1000*(current level)(in case of level 4, it's 4000). So 6000+4000 = 10000. Thus you need 10000 to get to level 5. But since you already have 6000, you "really" need only 4000.
(See this table for a list
http://www.monkeysushi.net/gaming/DnD/XP%20table.html)
The actual mathematical formula goes something like: XP required for next level = 1000 * [level + C(level, 2)] where C is the combinatoric funcion.
EXAMPLE: How much XP does a 28th level epic character have? At least 1000 * [27 + C(27, 2)] = 378,000 XP.
c) Probably a bug.