(a) correct. The lack of an ability score increase offsets the advantage of choosing whatever weapons, maneuvers and techniques go into your style. If you also got an ability score increase no one would ever take any of the fighting schools listed.
(b) i am somewhat less sure with the spell rune. But yes. I think you can cast a primal spell out of a spell rune even if your PC would not have access to that arcanum (because you practice a different arcanum). Its the rune that is channeling the “mojo.” Your PC is just activating it. As an aside I would note that it says “spells” so as written you couldn’t put a psionic “power” into it.
No one official, just my 2 cents.
