Yes I took a screenshot of the advert.Looks like the caravan is repairable but I would not rust the dealer given what you have said so far. The caravan sounds to be nowhere near what the advert must have said so mis description would be an added problem for the dealer. I hope you have a copy of the advert to show what the dealer said in it. I would probably still leave it to the card company as they should be easier to deal with.
I can see no basis for putting the caravan into storage and trying to recover the cost so I would not do that, but if you do you will need to get your insurers approval.
I was just thinking if it seems as if it's going to drag on, I could put it in storage and buy another so I can get on with my house renovation plans. It's a huge beast (twin axle 25' long) and there's no room for two!