Try the HVAC recalibration to your controls see if that helps with the heat problem. Low temps reading is good, normal range for the Kappa. IF it gets to 230 reading, not so good.
If you still have no heat after the recalibration is done, you could have other problems with it, the heater core that might have to be checked out?
With the base model 2.4 you should be able to run 87/89 octane with no problems. A tank full of 91 once in awhile is not a bad thing, if it is not too expensive for you? Good to save money now, just in case something goes wrong later. Kappa is not the cheapest thing out there to repair, on occasion that something major goes wrong with it. I would find out what service has been done to it, by the previous owner/dealer, as a base line history for future maintenance reference through a GM dealer by your vin#.
Enjoy the ride and the premagrin.