(1) I take my water to 015 ppm before i change my resin.
(2) I prefer Jets myself, Brush heads might be an idea to look at Ominpole and Ionics brushes as they dont hold any dirt cant rember the name of them, not sure if anyone sells them.
(3) What every happens dont go near Vents your get runs for every and every, also dont touch the brick work same thing will happen.
Justin