Well in my opinion, the body damage is a deal killer for most, as many people don't want to take a older car in to get repaired, second the engine is knocking. I have seen way too many deals I have passed because of a knocking engine. Fixing/rebuilding a engine is not fun, and most don't bother, even if they have it taken to a repair shop.
Based on my assumptions, I am gonna say it has around 150k+ miles, and if you are in a salt state, it has rust, so my estimated value you can sell it at is -
$700-900 at the most.
Of course $900 is assuming that the tranny is also in good shape, if not, then around $700 is what I would pay.
EDIT - Also, the KBB for the car in this condition is WAY off. No one would pay $2100 for a car that needs a engine and body work.
Just so you know.