Very Nice Boat - Good Choice.
Agree about a 2nd vehicle. 10 year old discovery would be a good purchase, you would need to win the lottery to keep it running through
- My sisters selling hers (about 8 years old) as they can't afford to keep replacing gearboxes! It does spend most of its life off road (in the dealers!)
I would have thought that most things would tow a 6m (750-1000kgs?), you can always use a rope on a steep slip - car at the top on the dry stuff etc.
As for it being stolen, make sure you tell your insurance everything (and then twice) 'cause they will find any excuse not to pay.
Keeping it at a marina increases security remember although you have insurance you never get back what you have lost, so extra costs in mooring is essentially going towards extra insurance payments.
By the time you buy a 2nd car, insure it, tax it, service it, tyres, petrol etc you may find a decent marina is the answer.