I want to tow cars from my paid reserved spot
Why do you want to two those cars?
The spot is paid and the owner was stupid to let others park there
I understand your frustration, it's okay to expect to use what you pay for. You should have them towed.
I'll just threaten them with getting towed.
I think you could go about it in a nicer way but you shouldn't feel bad for expecting to be able to use what you pay for. That spot should be yours.