How do I stop my LED strip from getting too hot?
A "12V" automotive electrical system generally supplies about 14V +/- 0.5V when the motor is running. Try putting some series 1N400x (where x = 1, 2, 3, 4, 5, 6 or 7) diodes in series with the strip. Each will drop about 0.6V, so three or four of them in series should make quite a difference. They're inexpensive, so get a bunch. 

The current is not simply predicted by Ohms law because the LED strip is a nonlinear load- the current rises much more quickly with increasing voltage than would the current through a resistor.