The red key is the master key so adding keys with out this is a more of a ball ache... As regards security, fit a physical immobilizer. Go to the police explain the situation and that he has hinted that it might get stolen (with the keys he has) or go to your insurance company tell them. this will cost you 2 years NCD though, but you will get a new set and the old set will no longer open the car.

If you know anyone at FORD you might be able to get a new lock set, Keys and ECU reprogram not too expensively!