The load numbers seem a bit high for your ~27F 9
9% outdoor design temperature. Was it calculated by the HVAC installer, or an engineer/architect? I'd expect a new code-min house to come in at about 7-8 BTU/hr per square foot for a radiant house that size, rather than ~9 BTU per foot.
ASHRAE recommends ~ 1.4x oversizing for fossil burner boilers, and that's probably where the (41K x 1.4x = ) ~58K number come from. But that's to deal with trading off efficiency vs. comfort a the 25 year low temp, etc. From an efficiency point of view oversizing doesn't really matter much with electric boilers, but there's really no need to oversize by more than 1.2x.
In your location controlling the room air temps with modulating ductless air source heat pumps and the floor temps with with an electric boiler operating off a floor thermostat usually makes economic sense, cutting the heating power used typically by more than half. It would offer high efficiency air conditioning for the 2o minute per year you might actually NEED it.