WHY IS MY TRAC OFF LIGHT ON, AND MY CAR IS SHIFTING HARD

First thing I would do is not let your boyfriend work on your car anymore. JK! lol. Hot wiring any component on a newer car is more dangerous and costly than just taking it to a reliable mechanic and paying to get it fixed right. You probably have a couple of things going on here, one being you could have blown fuses for the trac light and hard shifting caused by the wiring your boyfriend did. The rotten egg smell could be a rich condition caused by a ruptured fuel pressure regluator diaphram. Worst case is that he fried part of the computer control system. I would recommend taking it to a certified technician and getting it fixed. Search the bbb site for a highly recommended shop and stick with them.