If the answer to all of these questions is yes, don't sweat it. Chasing and humping usually subsides once the guinea pigs have their social order worked out. Usually, when I place 2 boars together after proper introductions, they make a mess of the cage for the first week chasing and humping each other.
One thing you don't want to do is separate them just because of normal dominance behavior. Then they have to start all over again.