Isn’t it pretty much accepted that the SR+ has a 60 kWh battery?
Tesla Model 3 Battery Pack & Battery Cell Teardown Highlights Performance Improvements
17.3 wh * 4416 cells = 76.4 kWh long range
250 * 76.4 / 322 = 59.3 kWh Sr+
How much is actually usable? Smarter people than me will comment on that.
As far as range vs energy consumed, I have to dig up some data but lots of conditions can affect how far you actually go vs what is predicted (wind, incline, speed). Did the card show energy rate as 159wh/km? I believe the EPA ratings are 230 wh/mi or 142 wh/km so you were using energy at a rate of 12% higher than normal. That would be 331km instead of 371 and 220/331 is roughly 67% of total (which is inline with the 35 out of 50 you mentioned). Maybe the consumption card is strictly related to driving and doesn’t count hvac or heated seats and you used that other 10% on heating (5-6 kWh)? Seems high as the data I can find suggests 0.5 kWh for seat heater on low.
Let's Look At Energy Consumption Of Tesla Model 3 Heater
Sorry if none of that cleared anything up but it sounds to me like we are missing some data to explain what you are seeing. Have you tried plugging your route into abetterrouteplanner.com and seeing what the suggested soc is at the end (it defaults to 90% to start so easy calculate total % used)?