Richard,
You're right and wrong.
The insurance is good for what ever the tractor is worth at the time of loss, regardless of the payoff, for the term of the policy (until it's paid off). After that, you're on your own. If someone steals it, you burn it or you total it, while still owing one payment, it's covered at book price. If there's a dispute of what the tractor is worth, it will be appraised.
You have no liability insurance what so ever under this policy.
I reread the policy and since I'm not a lawyer I called my dealer. He said, even if you owe $1, it's covered for the value of the tractor, plus they pay pickup and delivery.
Billy