Artozi, the hot spot you mention is just where the CPU and motherboard in general is located isn't it? It gets pretty warm with me too, but I suppose that is normal. Nothing is broken with me.|
I also don't recommend opening these tablets for repairing yourself. Don't risk losing warranty.
As for charging...I never really liked the stock charger...It sucks and you know it... One is better of buying a proper one.
Battery life is a very subjective matter. Me too.. I only get 3-4h. But I have to add to the story that I run the screen at 100% most of the time and am in the High performance profile, which probably explains this.