Also when it is this cold out try doing a full glow cycle, turn the car off, and back on again and complete another glow cycle. I think for the year of your car you should hear a "click" when the relay turns off.
While you have the hood up take your voltmeter and check to see if your glow plugs are working ok.
Dieselgiant has a great write up for finding and diagnosing glow plug problems. Here is the link
http://www.dieselgiant.com/glowplugrepair.htm
Your hard starts may be something as simple as that.
What type of motor oil are you running in your vehicle? Up here in snow belt Erie PA it's 21* and I run 5w40 Rotella. It really helps a great deal with the poor engine when it is this cold out.
If you're up for the reading there are also a bunch of threads about doing a valve adjustment, timing chain goodies, and other such stuff about improving the start of a cold engine.
Good luck! Being stranded sucks, but being stranded at home is just a little better
Edit: Also how cold is it in where you live? Going by your location it's 52 degrees in Hill Country Texas. At that temperature you should be having perfect starts. You might have a bunch of dead glow plugs!