Comfortable heating for your home is NOT about putting in a big forced air furnace.
Concrete at internal living space temperature
The house walls and floors are all one huge block of concrete. Concrete is great at storing heat, ie once you have heated it up it takes a long time to cool down, particularly if it is separated from the cold outside air thanks to lots of insulation. Note that the insulation is mainly on the outside of the concrete walls. You don't want insulation on the inside of the concrete walls because you want the thermal mass tightly coupled to the inside air temperature.
To achieve the above, you should add about an extra 4" of polystyrene (EPS) to the ICF EPS on the outside of the wall, and you should cut away the ICF EPS on the inside of the wall.
But what heats the internal concrete?
Typically when people talk about the benefits of thermal mass they describe how sun coming through the windows heats the thermal mass that then slowly releases the heat over the evening and night. That passive solar heating is great, but the thermal mass can benefit you in other ways. One example is with a wood burning fire.
If you have a wood burning fire you know that it throws out a huge amount of heat, but the logs burn out all too quickly. In practice you can't be bothered or forget, particularly late in the evening, to go and add more logs so it goes out and stops giving heat. If you have lots of thermal mass then the temperature in your house will be nicely evened out. While the fire is going full blast, the concrete will stop you getting too hot, and after the fire has gone out, the concrete will keep you warm.
Heating the floors can be done ether with an electrical heating mat or using hot water carried by PEX pipes.
Concrete floors, ie the concrete structure, have in the past been used for radiant heat because of their high mass. It does however take a great deal of energy to bring them up to temperature, so embedding in the concrete structure is not the best way of doing it. A much better bet is to use what's called a low-mass radiant floor. With a low-mass radiant floor, some of the heat is fairly immediately used to heat the air of the room and some of it goes towards gradually heating the concrete structure of the house.