Did you actually see his mouth open (making the sounds)? I ask because some others have mistaken the sound of a snake passing gas for other issues too.
And the timing suggests "gas" too...it's 8 days after he ate, so about time that things might be moving...Not sure about him rolling off a 1" high log as a result
but I can see where that could happen...BPs aren't the most graceful climbers anyway. Your hot spot sounds about 5* too hot, by the way.
FYI, if that was my snake, I'd keep watching him for a while, to see if any symptoms are repeated. Really think he just farted loudly, some snakes do.