You don't have to retrofit anything at the moment. You need to do a thermal balancing and tackle the weak points of the house. You can also definitely do something with the heating.
At a flow temperature of 60 degrees, you will probably reach an annual performance factor of 2. Then you will need (considering losses from the current boiler) about 13,000 kWh of electricity just for the heat pump. That will also cost you around 4k per year for heating energy. You should lower the flow temperature as much as possible. There is still more to be done. Insulate all pipes and storage tanks of the heating system. Adjust the control properly. Insulate roller shutter boxes, adjust windows and check for tightness. Insulate the basement ceiling if present. And so on and so forth. You can already do quite a bit for relatively little money. If nothing else works, switch to a split air conditioning system that can also heat. At least then you have an annual performance factor of about 3. That is enough for the transition and may cost around 5k.