[RickOShay]

Umm.. I will add my two cents on some of these, which probably will not help you, or is wrong.. but here goes. 岩 vs　石 my impression has always been that 岩 has the connotation of being bigger than 石 or a least more mountainy or something.. Like I don't think you could say 池に岩を投げる.. I mean maybe you could but it would portray a different image than what people normally think of.. I think..

増す vs 増える.. .I am pretty sure 増す is transitive.. and 増える is intransitve.. when　が　is used with 増す i think it is just a subject marker. For me when I use を.. I use 増す.. and I would never use を with 増える。

and last one I will comment on　空の vs　空っぽの.. I have typically said 空っぽの when talking about somebody's empty brainless head, but the exact difference.. just wait for a native..