Your contract is what you signed when you took the job. You should have a
copy of that.
As long as you gave enough notice, you can leave anytime. It's employment at
will, nobody can force you to work longer or even long hours to begin with.
Your only responsibility is to hand over the work you have done, not "
complete" work by some random definition.
Again, you should only talk through hr. tell hr directly you gave enough
notice and all the data are handed over. What he requested is way beyond any
appropriate.