Anthony,
Any adjustments you may do to the fireplace to create heat will cost
in excess of $1500 for certain. That is a mighty generouse gift to a
landlord.

I hate to be voice of doom on fireplaces but most open fireplace let
heat out despite the damper when they are not being used, and they
really suck heat out when they are being used or any time the damper
is open. There are some things you can do to improve the efficiency
slightly during burn, but they will not counteract the loss you will
experience in furnace heat. My best advice if you are looking to save
heat and money in the winter. Plug up the chimney nice and tight with
a chimney balloon or chimney cap (dont rely only on your damper to
stop heat loss). tak with your landlord about how old the furnace is
and how efficient it is.