Should I have qualified for homestead exemption? I live in it and it's my only home. How do I fix it? Maybe I put in wrong taxable amount?

There is no such thing on a federal tax return ... so which state are you talking about ?   And which state form are you trying to fill in ??? 

The homestead exemption has absolutely nothing to do with any tax return - state or federal. The homestead exemption is basically an amount of the assessed value of your property as determined by your local property tax appraiser, that is exempt from property taxes.

For example, in my county the first $50,000 of the assessed tax value of my primary residence as determined by my county appraiser, is exempt from property taxes. This as nothing to do with my income tax return.