They haven't decided what to do about the ability caps. The recent Kickstarter update said that they'd have to look at those and figure out what to do.
The Traits only give +1 and stop because they're placeholder traits to test the system, an overhaul of the Traits is coming.
Sourcery does nothing in the alpha. I'm pretty sure that it's not going to be usable until a certain point in the main plot, after which it'll be another school of magic, and points will be required to learn it's spells. Eventually, you should be prevented from investing points until that time.
Telekinesis is not a spell, it's an always-on ability that lets you reach items. the more your skill, the farther and heavier items you can reach.
No way are all spells in the alpha, I'm sure a lot are being held back. No rogue skills yet, but with a dagger you can backstab. More archery skills will probably be added as well.
