I was aware that LFP had range reduction in cold weather, just not the extent of it. I like the idea of LFP chemistry batteries but after having the Gen 1 ZS EV with a WLTP range of 163 miles I now prefer longer range capability even if I only need it a few times a year. Personal choice.
Slightly contradictory strategies there, not being in a hurry but tanking along at 75
I used to be very much like you, motorways were done at speed, cruise set at 80. However my first EV with the lower range forced me to slow a little to eke out the miles. I now set it at 65 and actually find the journey more enjoyable now.
Like on rapids as it's quicker to get off at 80% ish and do another charge later, it's sometimes quicker to go a bit slower.
Instavolt are now on Electroverse, so whilst they are horrendously expensive, you can at least save a few pennies using that card/app.
I find WattsUp to be good for checking live availability on route. Set up any chargers you're thinking of using as favourites and they display as a list on the home screen.
Although it is far better to plan and have alterative strategies, I'm sure the journey will be uneventful. What with our climate nowadays it will probably be a balmy 12 degrees at Xmas and no range worries.