This is Turtle.

What you need to do is get a Service tech out there and set your heat
Rise to about 50 degree F and find out at what speed it should be at.
heat Rise is the difference between the air going into it and the air
coming out.

Now speaking off the hand and no facts to stand on. Set it up higher
and see how it does but you will have to try to measure the heat rise
to not get it too low. 29 degree F or less would be too low and nothing
over 65 degrees F. differencial or heat rise.

Now speaking off hand here , if you can increase the blower speed it
will get the heat out to the rooms faster and then cut off faster. So
it would help a little to speed the blowers.

Now the out door thermostats is for another post here after you get
this right.

TURTLE