It all sounds completely wrong to me. When the car is sat on the road you should be ideally mid stroke. When the car is jacked up giving full droop, the springs should not dislocate. Any voids should be taken up with helper springs if you're not wanting to use a longer spring.
If your damper is topping out then it won't be long until you have catastrophic failure of the unit. The piston could come off the rod or you could pull the top closure off completely. If I were you I'd be going back to Gaz