Pedialyte contains sugar, I always wonder why it is suggested to re-hydrate diabetic hamsters. That's probably why you've found his sugar to be at its lowest rather than a change in the condition. The extreme weightloss is probably linked to the ketone spike, using body fat as an energy source (gluconeogenisis) produces high levels of ketones.
I guess with the heat dehydration will be more of a problem and might be why he is so lethargic, but even when the diet is controlled the lifespan of a diabetic hamster is considerably shorter so sadly it may just be his time