He is young, and you have a great window of opportunity to develop good eating habits now.
Unfortunately, Mac & cheese, Spaghetti-Os and even the Gerber meals are some of the worst things you can give your child because they're all very high in sodium, have very few vitamins or other nutrients.
He'll eat when he's hungry, and if you have several options available to try over time, he'll learn to like them. My kids (2 and almost 4) will eat broccoli just about anytime, and it's on their plates at least 2-3 times/week.
Fresh is usually best, though frozen vegetables can have more nutrients because they're frozen immediately after picking vs. the time it takes to get to the grocery store. Canned is usually awful because of added sodium and sugar to preserve the food.
At 13 months, there's really nothing he can't have other than foods that pose a choking hazard. I'd get things like lunch meat (ham, turkey) and american cheese from the deli and offer those at lunch (neither of my kids liked bread until older). keep fresh fruit around. Apples, bananas, grapes, pears. Babies can gnaw on a slice of apple or pear for a while getting the juices and fiber from the meat of the fruit.
Things like chicken nuggets are usually pretty bad, but Jamie Oliver has a great recipe on Oprah.com.
Try scrambled eggs, string cheese, yogurt.
Just about anything in a diabetic cookbook is going to be relatively healthy - and, almost all recipes are online and free.
Good luck! The earlier you start, the easier it will be!