No mate, this is not normal. As a general "rule of thumb", you should be able to drop the pH approximately 1 unit from gas on to lights on. For very high KH the number might be 0.7 units (or similar) but it must definitely move.I have measure the pH now and its on a steady 7.0 ( i think the other measurments that i presented were not right since the pH has been 7.0 for a long time). With 11dkH, its normal i think.
No, you cannot play ping-pong with water. It does not cooperate unfortunately...The idea to have filter outlet and the pump in those positions was to have a flow from left to right in front and right to left in the back, in order to have a kind of round water movement in the tank.
Cheers,