I love yogurt and the SV stick is perfect for that. My thoughts on your method:
The fat content of your starter yogurt doesn’t matter.
You heat the milk in a put briefly 82℃. I would put the milk in a metal container and use the SV stick for that. It’s more accurate. May take a bit longer though, but you can walk away, it would burn.
And while you heat the milk, why not longer? If you heat the milk at 82°C for 30 Minutes or so there is a protein breakdown (so I’m told) and this will result in a firmer yogurt.
For the yogurt itself I use 43°C@9h
After that I let the glasses cool down a little and then they go into the fridge.
There is no risk of any glass cracking, the temperature difference is too small for that.
BTW, if something goes wrong (yogurt stringy/slimy) do not throw it! I freeze it and whenever I make bread I put it that yogurt. It makes the inside of the bread softer and it raises much better. Unfortunately with the SV stick yogurts seldom go wrong.