Welcome to Yorkie Talk. Happy to hear little Harley is feeling better. You can post a picture here on your thread and also in the picture section (if you need help on how to post a photo, there are 2 "sticky" threads with instructions in the section):
My Yorkie Pictures! - YorkieTalk.com Forums - Yorkshire Terrier Community
I would stick to the kibble he was eating for awhile. Don't let what you read online about commercial foods panic you.
There is a wide range of opinions on what the best diet is for dogs. Here on Yorkie Talk, you will find dogs who thrive on kibble, homecooked, raw, and some other variations. Dogs have more specific nutrient requirements than humans. Puppies need more than adults. As Yorkiemini indicated, if you decide to homecook in the future, you should use a supplement like BalanceIt.
I would not be concerned about allergies. From what I have read here from people experienced in this department, a very small percentage of allergies are food related.
Some dogs simply cannot tolerate some foods. My Yorkie boys do not do well with carrots, green beans, apples, and other popular treats for Yorkies. Teddy cannot tolerate the smallest piece of egg.
Always test new foods slowly and in very small quantities.
Finances for vet bills: there is information in the library here about insurance plans. You can also look into Care Credit, which is a credit card with zero interest for a designated time period on qualified purchases (usually over $200). Your vet's office determines some of the terms.
Best wishes.