Can I ask something about PA state taxes?

I don't understand about tax forgiveness of a form PA40-SP.

I understood that if married couple's income were less than 13,500, they could apply their tax forgiveness.
So we didn't apply about tax forgiveness for 3 years. Is it right?
We don't have children and my husband is researcher in University( we're non-resident). Also, I don't have any job. (any income)
My husband's income is less than $33,000. I don't know can we refund some money from PA state. Should we fill out a form PA40-SP?

Thanks!

You need to give the PA tax authorities a call and ASK!