In less depressing news, our yogurt turned out fabulously; it tastes delicious and the consistency is very smooth and thick.
Here's the recipe:

1 quart of milk
1/4 cup dry milk
1/2 cup plain yogurt (as a starter)

Heat the milk and dry milk in a saucepan on the stove to about 185 degrees (F). Let it cool to about 110 degrees (F). Stir a little of the cooled milk into a glass measuring bowl with the yogurt starter. Add the rest of the milk and stir gently. (Do not whisk.) Pour into glass jars with lids and set in warm stove* for about 8-10 hours. Remove and place in fridge for 2 hours to finish firming the yogurt.

Add your choice of sweetener to the yogurt before eating, such as fruit, jam, maple syrup, or honey.

Save some yogurt to use as starter for your next batch.

*Our gas stove's pilot is always on, so I can't say the exact temperature; it's about 100 degrees (F), we think. But it really just needs to sit in a slightly warmed space, so the yogurt culture can grow.