If your snail is climbing out of the tank, she is more than likely looking for a place to lay eggs. Just lower your water line an inch or so, apple/mystery snails lay their eggs above the water line. If the water covers the eggs, they will drown.
On the shell erosion, you can also buy cuttlebone that is used for pet birds, it is real cheap at Walmart. I break off pieces and put it in the filter until it is water logged and then drop it in the tank.
Everything else sounds like normal behaviour. If you have to handle your snails, coat your hands with water conditioner first.
First, Do No Harm!