We have a much-loved Rhodesian Ridgeback who although not listed here as one of the seven dangerous breeds has all the characteristics....he is a very big boy but like your dog, a big softy.
He has a passport, microchip, all the injections/vaccinations required, our house has 2m- high walls (he never goes out when the gate is open, though...a real home-lover), is registered with the appropriate local authorities -he has his tarjeta
with his details and we have 300000 euros-worth of liability insurance for him.
We repeatedly tried to register him as a dangerous dog because he has those characteristics but our vet and the local police, including officers from the local Police Dog Unit, told us it was unneccessary as we had done everything required, according to them. So we let matters rest. He is a great favourite with our local police who call out 'Hola Guapo' when they see him (sadly they are not referring to me....
When we take him to public places he is on the lead and muzzled. He runs free in the campo unless we come across other dogs whose owners have them on a lead. Then we restrain him too, not because he will attack but because we understand that his size can be menacing to some people and dogs. He has been bitten several times by smaller dogs but has never retaliated.
So if you have the passport, chip etc. and take the usual precautions a sensible dog owner would you will most likely have no problems. I help run a dog rescue charity so know many Spanish and non-Spanish owners of medium or large-sized dogs and not one of them has registered their dog as dangerous.
You can see photos of Our Little Azor in my album.
Of course sensible people know that there are no 'dangerous' dog breeds per se. All dogs are capable of aggression and can cause damage. I have been bitten by a Jack Russell! The dangerous ones are ignorant, irresponsible and sometimes thuggish owners who often see their dogs as status symbols or even weapons.