Bill wrote:

So what I would do for now is to get the largest heating unit you can get,
and zone the house out. Instead of heating the *entire* house, figure out
which rooms or which portion of the house can be heated while leaving the
rest of the house unheated. (Close doors.) Perhaps you can move your office
elsewhere for the time being?

Installing "the largest heating unit you can get" and then closing off
registers to keep some rooms unheated is a good way to decrease the
lifespan and efficiency of the furnace, making your wallet much lighter
in the long run.

The furnace must be sized for the particulars of the zone(s) it feeds.
If it is desired to have part of the house colder than another, they
should be on separate zones by design.