car wont start

Do you hear anything like a click or something? If not then you need to make sure that the purple wire on the Starter Solenoid is getting a trigger signal ( voltage ) from the ignition switch. if not , then you need to do some electrical tracing. Same thing with your light problem, if no power to the headlamps, then see if you have power to the head light switch etc.

you should change the whole switch from the key terminal

Check the grounding from the battery to the body by Metering across the positive and the firewall should have around 12 volts also Make sure there is a Ground bond between the body and the engine. that would cause your starter not to function. If all the grounding is proper Begin Tracing the positive out. should have a main to the starter and one to the fuse block through a terminal splice.