My dog looks nothing like your description, but he does look exactly like Toto from The Wizard of Oz; even other cairn terrier owners mistake him for a cairn. His ears aren't folded over, they are permanently pricked up. And he barks all the time. His coat is long and thick. He was the only dark brown dog in the litter, and had a very short coat until he was 6 months old.
He is probably the most intelligent dog I have ever owned. As you mention in your description, he is also stubborn and independent, and loves being the centre of attention. He has a repertoire of cute behaviours he trots out if people aren't paying him enough attention.
If it's alive, it's a potential friend. He gets on fine with our cats, tortoises and lizards. Plus every other dog and cat he has ever met. Birds are for barking at, though, especially if they have the temerity to fly over 'his' airspace, or sit on 'his' roof.
If I am working on the computer or watching tv, and therefore not playing with him, he will deliberately push his ball under the settee and cry piteously until I retrieve it for him. Then as soon as I sit back down, he'll push it under again.
He is a total water baby. His idea of heaven is to swim after balls in the river. Balls are his favourite thing, as soon as your eyes are open in the morning he is there with a ball in his mouth, waiting for you to throw it. You then have to throw or kick it for him all day long, and he even takes it to bed in case you wake up in the night.
He is generally willing to please, and does enjoy sitting watching films with me. Particularly if there are animals in it he can bark at.
He does think all food should be for him, though. I've seen him take rocket leaves from a tortoise's mouth and eat it. He has to be told to leave it, so that they get to eat. Although he is not a greedy dog, and will only eat his own food when he's actually hungry, and is happy to leave some if there is too much. He just doesn't see why other pets should get fed too. I
Overall, he is a delight. I can, and do, take him anywhere and everywhere, because I can trust him to behave himself and not be a nuisance. The fact that he doesn't shed hair is a definite plus - I am used to wearing my dogs to work, and with him, for the first time ever, I don't have to!