You normally do not insulate between rooms. Insulating a ceiling with a heated room above is pointless.
I would suggest if your windows are old, placing the plactic on the inside that streaches with a hair dryer. Windows are often the single biggest area of heat loss.
Second, insulate the attic floor well with as much as 12" of insulation. Prevent heat loss out of the top of the house.
Plus all the good advice from "The Insulator"
Good luck & stay warm.
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