". . . what should I list it for & how do I convince people it IS worth more than $20,000 . . ."
That would be the job of the Agent you hire . . . . if you actually list it.
Can the Parcel still be sub-divided into 8 lots with the new Well positioned where it is ?
Will all 8 lots perc for individual septic systems ?
If that parcel were here, I'd probably tell you that "the sum of the parts is greater than the whole"
. . . . with each legal building lot being worth about $15,000 to $20,000. Some people don't have the stomach for the uncertainty of doing a sub-division; but the rewards can make it quite worthwhile.
Why didn't the prior Owner sub-divide it before selling it to you ?
What will the Tax consequences be in Florida if you sell it for a big profit after owning it for a mere 12 months ?
It won't be as private once 8 new homes are built on it.