CAR WON'T START UP?

Ok:
No it shouldn't have caught fire. If it did, there is a good chance something may have happened with the ignition timing. Also, that is a good indicator that you are getting spark.

To check for spark, remove a spark plug and reattach the plug wire to it. Next, ground the steel part of the spark plug against something steel on the engine. Have your wife crank the engine (don't touch the plug while she is cranking). You should get a spark at the end of the plug that goes into the engine (the electrode). Pay attention to the color of the spark. It should be a blueish color if it's strong.

As far as fuel line freeze-up, yes I agree with you. First, it rarely happens and @ 50 degrees, you would have been fine by now. Also, is the check engine light on or is there a security light coming on?

Joe