Does Sasuke have only one Rinnegan eye because he only got half of Hagoromo's chakra?
That is partly the case. You see, Hagoromo is the son of Kaguya, the fruit of chakra. So, he is the descendant of the creator of chakra. He creates the yin release and yang release. Naruto gets the yin half, while Sasuke gets the yang half. Anybody with the yang half can get the special type of Rinnegan, called the Magatama Rinnegan (I think).