My federal tax return lowered to about $600 after I canceled the amendment. But I am claiming a child.

The fact that you are claiming a child does not guarantee a big refund.  Your child-related credits are based on how much you earned from working.

Look at your 2018 tax return to see the child-related /dependent credits you received:

Child tax credit line 12a

Additional Child Tax Credit line 17b   (schedule 8812) 

Credit for Other Dependents line 12a

Earned Income Credit (EIC) line 17a

Child and Dependent Care Credit line 12     (comes from Schedule 3 Form 2441)

The dependents you listed are on the first page of your Form 1040 below your address.

https://ttlc.intuit.com/questions/1900923-what-is-the-child-tax-credit

https://ttlc.intuit.com/questions/1900643-what-is-the-child-and-dependent-care-credit

https://ttlc.intuit.com/questions/1899157-what-are-the-qualifications-for-the-earned-income-credit-eic-or-eitc

https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit/use-the-eitc-assistant

https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-cre...

Why were you amending and why did you "cancel" the amended return?