Welcome to the crazy world of camping!!
The noseweight is the downwardload on the towball, car & van makers both give this figure in their handbook, which can be anything from 75kg-100kg whichever is the lower figure that is the one to go by,IE: if car has 75k and van 100k then stick to 75k. the ideal is about 7% of the acual laden weight of the van,
To find if your car is able to tow your van, find the kerbweight of the car(in hand book)Devide this figure by 100 then multiply by 85 this will give you 85% recomended towing limit.If you dont have handbooks , use a public weighbridge about a fiver or so,
I am assuming you are new to towing if so, I would highly recomend a towing course with the Caravan & Camping Club,
I hope this is a help, anything else come back,
Enjoy It is great fun..