How do I get confirmation that I qualify for free (via Fidelity Investments) Federal and State returns up to April 15th?

The only discount I was able to find for TurboTax and Fidelity is a $20 discount.

See How do I get my TurboTax affiliate partner discount? 

Do you know if the your discount is valid up to April 15th?

No, you would need to contact Fidelity to see when their discount is set to expire.