I heat 1500 sq ft shop floor to 75 degrees with a wood boiler. Some days if its sunny and calm it will get to 70 in the shop. Cold windy days it may get down to 60. I will have to turn it down when we start getting 50s outside. I love the warm feet and how you can have a door open and not be cold. I did 2 inch foam under nothing on the sides but a block wall. I loose some heat cause of that. It takes a half if not a full day to get a noticeable air temp change. I think with your system you need to let the floor temp alone and if you want to regulate heat you will need to do it with a hot air heater.
I did figure with my system running I was putting 60000 btu to the floor. I don't have a timer to tell me how long it runs so I don't know how many but I really put into the shop in a season.