David, If you are going to raise the front to a height higher than the lift of the jockey wheel then do as follows. Drop the jockey wheel through the clamp till it hits the ground with it fully retracted, then raise but stop before it can unscrew fully (and fall apart). Drop both front steadies to take the weight of the van and screw the jockey wheel in again. Drop it further through the calam and start lifting again.
If you get to the stage that the jockey wheel has been dropped through the clamp as far as possible but you want to lift it more then lower the steadies further and place a breeze block or similar under the wheel. Keep an eye on the rear of the van to make sure it doesn't bottom.
You could remove the jockey wheel from the van, unscrew it, then screw it in an inch, then mark the position, so that in future u dont go too far again, a majic marker or even insulating tape stuck round it will do.
You have been lucky, sometimes the thread gets damaged & it wont screw back together again,
Sometimes u can file it back to shape, but if its the nut on the bottom half that deformes its a new jockey wheel unfortunatly.