Simple answer:

The 4075 is the maximum train weight, so your towing combination must weigh less than this. 2200 is the Max. laden weight of the Omega, so worst case, you can subtract 2200 from 4075 and you end up at roughly 1875

An empty Omega weighs about 1750 - 1850 kg, so if lightly loaded you might get away with a little more, but it would generally be unwise to tow more than the car itself weighs. Not sure about caravans but most twin axle trailers are plated for more load than the Omega can tow, so if a caravan has to be twin axle, it's probably marginal or overweight.

I'm not sure if an official max towing weight was published in the Omega's specifications, but the above will keep you legal at least.

There are also license limits as to what you can tow. These would be significant if you have passed your test since around the mid-90's and don't have the B+E entitlement on your license.

Anything above 750 kg needs to be braked.