Take a look at the original sentence again:
Ingie looked at his wife's collection of cookbooks and
sighed, although there were thousands of
recipes for delicious meals, he knew Valerie would want to order another
pepperoni and mushroom pizza for dinner.
You chose to fix it the correct way:
Ingie looked at his wife's collection of cookbooks and
sighed. Although there were thousands of
recipes for delicious meals, he knew Valerie would want to order another
pepperoni and mushroom pizza for dinner.
Ingie looked at his wife's collection of cookbooks and sighed is a complete sentence. Although there were thousands of recipes for delicious meals, he knew ... begins the second sentence. You are always correct when you use a period between the two complete sentences that create the comma splice.