Heather, take away the baby food! As long as you continue to serve it, he won't take the challenge to move on. Start with foods that have texture but are soft, like toast and scrambled eggs, which require him to learn to chew before he swallows. He will probably give you a hard time for a day or two, but you shouldn't back down.
By not eating enough table food, your son's not only lacking variety in his diet–he's not developing his jaw muscles appropriately. Unless there is a physical reason why he can't progress to table food, there is no reason for him to stay on baby food. Continue with the yogurt, pudding and applesauce but consider juice-based frozen pops instead of the regular ones, which provide no nutrition.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.