Seeing your woes, I think you have either received a faulty device or you are a reckless user (which you denied).
I'm having cool functioning on FOTA 5, but while charging it's an Iron Box. Even on gaming, it's cooler than the charge temperature.
You also say you have miserable battery life, but everyone else has really decent battery life and some have really great battery lives too.
And I personally think this was because of technical complications. Smartron has done a great job with SW so far at least according to me as I've done comparisons with my friends' MiA1s, J7s, J5 and Redmi Note 3,4,5 and the srt has better working than all of these, smoothly running any app, while others failed to open 90% 3rd Party apks, lagging with fundamental functions and stuff like Live Wallpapers and Launchers. I think that will run with Oreo too and they might be trying to give the best Oreo UI so far in any phone.