I think most believe the Hyksos were semitic, but it is not absolutely established. The Egyptians already had bronze tools, but you are correct that the Hyksos introduced the chariot to Egypt.
That the 15th dynasty is earlier than the usual date given for the Exodus is correct. Some think that after their rule was overthrown by the Theban dynasty, many Hyksos may have stayed in Egypt as servants, mercenaries, settlers, etc., with some of them later moving out of Egypt giving birth to the Exodus legend.
Many scholars think the Exodus may have been during the 19th dynasty, which was native to the eastern Nile delta. There is reason to believe that dynasty may have been part Asian. Ramesses II had red hair and they seemed to favor Asian gods. Many scholars think the pharaoh of the Exodus was Ramesses II. In the de Mille film, Ramesses II was played by Yul Brynner.
So, my point was that many think there may have been a connection between the Hyksos and the Exodus, but later than the 15th dynasty. I should have made that clearer.