1) No Uchiha were left, with exception of Sasuke. All of them are dead and their bodies have been found, except Shisui.
2) Shin does not have the trademark Black hair. I know a point about Naruto's hair can be made, but if we assume Salad is an Uchiha, even after being an half Uchiha , she has black hair.
3) About Shin's sharingan , he is yet to exhibit a sharingan tech. Also it is seen that Mr. Hooded has a Sharingan and has possibly linked his sharingan via chakra rods. He may be sharing vision with Shin and Jubbi clone
1.How do you know that no Uchihas were away from the village or on a vacation or something like that when the massacre happened?
2. Point number two uses the same bad logic as that guy who says that Bolt isn't Hyuuga. First of all, black hair is not actually a genetic trademark of the Uchiha. It was never stated in the manga, anime or databooks that all Uchihas have black hair. Sarada didn't inherit black hair as an Uchiha trait. She inherited black hair simply because her father has black hair. Black hair is not really an Uchiha trait. It is just that most Uchihas that we've seen have black hair. Here is proof that not all Uchihas have black (yes these Uchihas are canon):
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(look at his picture)
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(notice the red haired Uchiha in the picture)
3. You say he has yet to exhibit some sharingan techniques, but without mangekyou, there really aren't many "sharingan techniques" to be used. Think about the techniques of the standard sharingan for a minute:
copying jutsus
the hypnotic eye
increased perception
genjutsus
izanagi
izanami
Now consider this:
Be honest, those first 3 abilities became irrelevant after part 1. No Uchiha real or fake really uses those anymore.
Izanagi and izanami are special circumstance one time only jutsus that not all Uchihas even know. Plus, they make you go blind.
Genjutsu is the only one of those that is often used anymore, and even then it is mostly used by Uchihas that really specialize in it like Itachi. Madara, Obito and Sasuke use it from time to time, but genjutsu is not exactly their first resort. If even those experienced rikudou level Uchihas such as the 3 I just listed rarely use genjutsu, then what makes you think that an inexperienced little boy would be pulling out the genjutsu?