If you are towing the insurance covers you against third party claims involving any trailer. If the trailer was unroadworthy then there might be problems, but there is no problem with that at the moment. I assume that the caravan is at your home so the point of causing a fire is probably not yet relevant. Before spending more money on the project I would try and find out what you would need to do to make it acceptable to insurers.
The certificate of conformity point only refers to caravans manufactured from 2012, and I assume that this does not apply here.
Having said that there are problems not only with making sure that anything you fit is lightweight, but also that the furniture can be part of the structural integrity of the caravan, particularly, newer models. That would mean following the original plan in the main.
You will also need to be competent in handling the gas and electrics or have help from someone who is.
If you say what you have bought and what your plans are then there should be some help available. Good luck though.