2. We have no geothermal sources sufficient for production of electricity, it can only be used to slightly reduce primary energy use during winter, but it will raise electricity use during winter.
3. Helps not at all, because 0 times however large number you like is still 0.
4. Likewise.
5. Improvements in efficiency do not help you stay alive when it's -30°C.
The option up here really truly is "do we use fossil fuels, or do we use nuclear". Renewables do not help. They are nice to have, and it makes sense to build them because they complement the reduced output of nuclear in summertime, and because the lower cost/kWh can help some industry, but that's all.